diff --git a/core/modules/system/src/Tests/Form/CheckboxTest.php b/core/modules/system/src/Tests/Form/CheckboxTest.php
index 3e0240c..b913f5e 100644
--- a/core/modules/system/src/Tests/Form/CheckboxTest.php
+++ b/core/modules/system/src/Tests/Form/CheckboxTest.php
@@ -32,7 +32,7 @@ function testFormCheckbox() {
       // #return_value, with the exception of integer 0, which is not supported.
       // @see form_process_checkbox().
       foreach (array('0', '', 1, '1', 'foobar', '1foobar') as $return_value) {
-        $form_array = \Drupal::formBuilder()->getForm('form_test_checkbox_type_juggling', $default_value, $return_value);
+        $form_array = \Drupal::formBuilder()->getForm('\Drupal\form_test\Form\FormTestCheckboxTypeJugglingForm', $default_value, $return_value);
         $form = drupal_render($form_array);
         if ($default_value === TRUE) {
           $checked = TRUE;
diff --git a/core/modules/system/src/Tests/Form/FormTest.php b/core/modules/system/src/Tests/Form/FormTest.php
index 88acb40..f113bcf 100644
--- a/core/modules/system/src/Tests/Form/FormTest.php
+++ b/core/modules/system/src/Tests/Form/FormTest.php
@@ -10,6 +10,7 @@
 use Drupal\Component\Serialization\Json;
 use Drupal\Component\Utility\String;
 use Drupal\Core\Render\Element;
+use Drupal\form_test\Form\FormTestDisabledElementsForm;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -158,11 +159,10 @@ function testRequiredFields() {
    * is submitted twice, first without values for required fields and then
    * with values. Each submission is checked for relevant error messages.
    *
-   * @see form_test_validate_required_form()
+   * @see \Drupal\form_test\Form\FormTestValidateRequiredForm
    */
   function testRequiredCheckboxesRadio() {
-    $form = $form_state = array();
-    $form = form_test_validate_required_form($form, $form_state);
+    $form = \Drupal::formBuilder()->getForm('\Drupal\form_test\Form\FormTestValidateRequiredForm');
 
     // Attempt to submit the form with no required fields set.
     $edit = array();
@@ -235,7 +235,7 @@ function testRequiredCheckboxesRadio() {
    * and then with value. Each submission is checked for relevant error
    * messages.
    *
-   * @see form_test_validate_required_form_no_title()
+   * @see \Drupal\form_test\Form\FormTestValidateRequiredNoTitleForm
    */
   function testRequiredTextfieldNoTitle() {
     // Attempt to submit the form with no required field set.
@@ -293,8 +293,7 @@ function testCheckboxProcessing() {
    * Tests validation of #type 'select' elements.
    */
   function testSelect() {
-    $form = $form_state = array();
-    $form = form_test_select($form, $form_state);
+    $form = \Drupal::formBuilder()->getForm('Drupal\form_test\Form\FormTestSelectForm');
     $error = '!name field is required.';
     $this->drupalGet('form-test/select');
 
@@ -366,8 +365,7 @@ function testEmptySelect() {
    * Tests validation of #type 'number' and 'range' elements.
    */
   function testNumber() {
-    $form = $form_state = array();
-    $form = form_test_number($form, $form_state);
+    $form = \Drupal::formBuilder()->getForm('\Drupal\form_test\Form\FormTestNumberForm');
 
     // Array with all the error messages to be checked.
     $error_messages = array(
@@ -484,7 +482,7 @@ function testColorValidation() {
   function testDisabledElements() {
     // Get the raw form in its original state.
     $form_state = array();
-    $form = _form_test_disabled_elements(array(), $form_state);
+    $form = (new FormTestDisabledElementsForm())->buildForm(array(), $form_state);
 
     // Build a submission that tries to hijack the form by submitting input for
     // elements that are disabled.
@@ -568,8 +566,7 @@ function assertFormValuesDefault($values, $form) {
    */
   function testDisabledMarkup() {
     $this->drupalGet('form-test/disabled-elements');
-    $form_state = array();
-    $form = _form_test_disabled_elements(array(), $form_state);
+    $form = \Drupal::formBuilder()->getForm('\Drupal\form_test\Form\FormTestDisabledElementsForm');
     $type_map = array(
       'textarea' => 'textarea',
       'select' => 'select',
diff --git a/core/modules/system/src/Tests/Form/ProgrammaticTest.php b/core/modules/system/src/Tests/Form/ProgrammaticTest.php
index 902fe2e..a5c4071 100644
--- a/core/modules/system/src/Tests/Form/ProgrammaticTest.php
+++ b/core/modules/system/src/Tests/Form/ProgrammaticTest.php
@@ -72,7 +72,7 @@ function testSubmissionWorkflow() {
   private function submitForm($values, $valid_input) {
     // Programmatically submit the given values.
     $form_state = array('values' => $values);
-    drupal_form_submit('form_test_programmatic_form', $form_state);
+    \Drupal::formBuilder()->submitForm('\Drupal\form_test\Form\FormTestProgrammaticForm', $form_state);
 
     // Check that the form returns an error when expected, and vice versa.
     $errors = form_get_errors($form_state);
@@ -106,7 +106,7 @@ public function testProgrammaticAccessBypass() {
     // Programmatically submit the form with a value for the restricted field.
     // Since programmed_bypass_access_check is set to TRUE by default, the
     // field is accessible and can be set.
-    \Drupal::formBuilder()->submitForm('form_test_programmatic_form', $form_state);
+    \Drupal::formBuilder()->submitForm('\Drupal\form_test\Form\FormTestProgrammaticForm', $form_state);
     $values = $form_state['storage']['programmatic_form_submit'];
     $this->assertEqual($values['field_restricted'], 'dummy value', 'The value for the restricted field is stored correctly.');
 
@@ -115,7 +115,7 @@ public function testProgrammaticAccessBypass() {
     // restrictions apply, the restricted field is inaccessible, and the value
     // should not be stored.
     $form_state['programmed_bypass_access_check'] = FALSE;
-    \Drupal::formBuilder()->submitForm('form_test_programmatic_form', $form_state);
+    \Drupal::formBuilder()->submitForm('\Drupal\form_test\Form\FormTestProgrammaticForm', $form_state);
     $values = $form_state['storage']['programmatic_form_submit'];
     $this->assertNotEqual($values['field_restricted'], 'dummy value', 'The value for the restricted field is not stored.');
 
diff --git a/core/modules/system/src/Tests/Form/ValidationTest.php b/core/modules/system/src/Tests/Form/ValidationTest.php
index 7fef3c9..d62d526 100644
--- a/core/modules/system/src/Tests/Form/ValidationTest.php
+++ b/core/modules/system/src/Tests/Form/ValidationTest.php
@@ -197,11 +197,10 @@ function testPatternValidation() {
   /**
    * Tests #required with custom validation errors.
    *
-   * @see form_test_validate_required_form()
+   * @see \Drupal\form_test\Form\FormTestValidateRequiredForm
    */
   function testCustomRequiredError() {
-    $form = $form_state = array();
-    $form = form_test_validate_required_form($form, $form_state);
+    $form = \Drupal::formBuilder()->getForm('\Drupal\form_test\Form\FormTestValidateRequiredForm');
 
     // Verify that a custom #required error can be set.
     $edit = array();
diff --git a/core/modules/system/tests/modules/form_test/form_test.module b/core/modules/system/tests/modules/form_test/form_test.module
index 34e6242..08fdb2e 100644
--- a/core/modules/system/tests/modules/form_test/form_test.module
+++ b/core/modules/system/tests/modules/form_test/form_test.module
@@ -5,14 +5,6 @@
  * Helper module for the form API tests.
  */
 
-use Drupal\Component\Serialization\Json;
-use Drupal\Component\Utility\String;
-use Drupal\Core\Database\Database;
-use Drupal\Core\Language\LanguageInterface;
-use Drupal\form_test\Callbacks;
-use Drupal\Core\Datetime\DrupalDateTime;
-use Symfony\Component\HttpFoundation\JsonResponse;
-
 /**
  * Implements hook_permission().
  */
@@ -29,28 +21,6 @@ function form_test_permission() {
 }
 
 /**
- * Form submit handler to return form values as JSON.
- */
-function _form_test_submit_values_json($form, &$form_state) {
-  $response = new JsonResponse($form_state['values']);
-  // @todo remove once converted to new routing system.
-  $response->send();
-  exit;
-}
-
-/**
- * Form builder for testing hook_form_alter() and hook_form_FORM_ID_alter().
- *
- * @deprecated Use \Drupal\form_test\alterForm()
- */
-function form_test_alter_form($form, &$form_state) {
-  // Elements can be added as needed for future testing needs, but for now,
-  // we're only testing alter hooks that do not require any elements added by
-  // this function.
-  return $form;
-}
-
-/**
  * Implements hook_form_FORM_ID_alter() on behalf of block.module.
  */
 function block_form_form_test_alter_form_alter(&$form, &$form_state) {
@@ -81,272 +51,6 @@ function system_form_form_test_alter_form_alter(&$form, &$form_state) {
 }
 
 /**
- * Form builder for testing \Drupal\Core\Form\FormValidatorInterface::validateForm().
- *
- * Serves for testing form processing and alterations by form validation
- * handlers, especially for the case of a validation error:
- * - form_set_value() should be able to alter submitted values in
- *   $form_state['values'] without affecting the form element.
- * - #element_validate handlers should be able to alter the $element in the form
- *   structure and the alterations should be contained in the rebuilt form.
- * - #validate handlers should be able to alter the $form and the alterations
- *   should be contained in the rebuilt form.
- *
- * @deprecated Use \Drupal\form_test\validateForm()
- */
-function form_test_validate_form($form, &$form_state) {
-  $object = new Callbacks();
-
-  $form['name'] = array(
-    '#type' => 'textfield',
-    '#title' => 'Name',
-    '#default_value' => '',
-    '#element_validate' => array(array($object, 'validateName')),
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Save',
-  );
-
-  // To simplify this test, enable form caching and use form storage to
-  // remember our alteration.
-  $form_state['cache'] = TRUE;
-
-  return $form;
-}
-
-/**
- * Form validation handler for form_test_validate_form().
- */
-function form_test_validate_form_validate(&$form, &$form_state) {
-  if ($form_state['values']['name'] == 'validate') {
-    // Alter the form element.
-    $form['name']['#value'] = '#value changed by #validate';
-    // Alter the submitted value in $form_state.
-    form_set_value($form['name'], 'value changed by form_set_value() in #validate', $form_state);
-    // Output the element's value from $form_state.
-    drupal_set_message(t('@label value: @value', array('@label' => $form['name']['#title'], '@value' => $form_state['values']['name'])));
-
-    // Trigger a form validation error to see our changes.
-    form_set_error('', $form_state);
-  }
-}
-
-/**
- * Form constructor to test the #required property.
- *
- * @deprecated Use \Drupal\form_test\validateRequiredForm()
- */
-function form_test_validate_required_form($form, &$form_state) {
-  $options = array('foo' => 'foo', 'bar' => 'bar');
-  $validate = array('form_test_validate_required_form_element_validate');
-
-  $form['textfield'] = array(
-    '#type' => 'textfield',
-    '#title' => 'Name',
-    '#required' => TRUE,
-    '#required_error' => t('Please enter a name.'),
-  );
-  $form['checkboxes'] = array(
-    '#type' => 'checkboxes',
-    '#title' => 'Checkboxes',
-    '#options' => $options,
-    '#required' => TRUE,
-    '#form_test_required_error' => t('Please choose at least one option.'),
-    '#element_validate' => $validate,
-  );
-  $form['select'] = array(
-    '#type' => 'select',
-    '#title' => 'Select',
-    '#options' => $options,
-    '#required' => TRUE,
-    '#form_test_required_error' => t('Please select something.'),
-    '#element_validate' => $validate,
-  );
-  $form['radios'] = array(
-    '#type' => 'radios',
-    '#title' => 'Radios',
-    '#options' => $options,
-    '#required' => TRUE,
-  );
-  $form['radios_optional'] = array(
-    '#type' => 'radios',
-    '#title' => 'Radios (optional)',
-    '#options' => $options,
-  );
-  $form['radios_optional_default_value_false'] = array(
-    '#type' => 'radios',
-    '#title' => 'Radios (optional, with a default value of FALSE)',
-    '#options' => $options,
-    '#default_value' => FALSE,
-  );
-  $form['actions'] = array('#type' => 'actions');
-  $form['actions']['submit'] = array('#type' => 'submit', '#value' => 'Submit');
-  return $form;
-}
-
-/**
- * Form element validation handler for 'Name' field in form_test_validate_required_form().
- */
-function form_test_validate_required_form_element_validate($element, &$form_state) {
-  // Set a custom validation error on the #required element.
-  if (!empty($element['#required_but_empty']) && isset($element['#form_test_required_error'])) {
-    form_error($element, $form_state, $element['#form_test_required_error']);
-  }
-}
-
-/**
- * Form submission handler for form_test_validate_required_form().
- */
-function form_test_validate_required_form_submit($form, &$form_state) {
-  drupal_set_message('The form_test_validate_required_form form was submitted successfully.');
-}
-
-/**
- * Form constructor to test the #required property without #title.
- *
- * @deprecated Use \Drupal\form_test\validateRequiredFormNoTitle()
- */
-function form_test_validate_required_form_no_title($form, &$form_state) {
-  $form['textfield'] = array(
-    '#type' => 'textfield',
-    '#required' => TRUE,
-  );
-  $form['actions'] = array('#type' => 'actions');
-  $form['actions']['submit'] = array('#type' => 'submit', '#value' => 'Submit');
-  return $form;
-}
-
-/**
- * Form submission handler for form_test_validate_required_form_no_title().
- */
-function form_test_validate_required_form_no_title_submit($form, &$form_state) {
-  drupal_set_message('The form_test_validate_required_form_no_title form was submitted successfully.');
-}
-
-/**
- * Builds a simple form with a button triggering partial validation.
- *
- * @deprecated Use \Drupal\form_test\validateFormWithErrorSuppression()
- */
-function form_test_limit_validation_errors_form($form, &$form_state) {
-  $form['title'] = array(
-    '#type' => 'textfield',
-    '#title' => 'Title',
-    '#required' => TRUE,
-  );
-
-  $form['test'] = array(
-    '#title' => 'Test',
-    '#type' => 'textfield',
-    '#element_validate' => array('form_test_limit_validation_errors_element_validate_test'),
-  );
-  $form['test_numeric_index'] = array(
-    '#tree' => TRUE,
-  );
-  $form['test_numeric_index'][0] = array(
-    '#title' => 'Test (numeric index)',
-    '#type' => 'textfield',
-    '#element_validate' => array('form_test_limit_validation_errors_element_validate_test'),
-  );
-
-  $form['test_substring'] = array(
-    '#tree' => TRUE,
-  );
-  $form['test_substring']['foo'] = array(
-    '#title' => 'Test (substring) foo',
-    '#type' => 'textfield',
-    '#element_validate' => array('form_test_limit_validation_errors_element_validate_test'),
-  );
-  $form['test_substring']['foobar'] = array(
-    '#title' => 'Test (substring) foobar',
-    '#type' => 'textfield',
-    '#element_validate' => array('form_test_limit_validation_errors_element_validate_test'),
-  );
-
-  $form['actions']['partial'] = array(
-    '#type' => 'submit',
-    '#limit_validation_errors' => array(array('test')),
-    '#submit' => array('form_test_limit_validation_errors_form_partial_submit'),
-    '#value' => t('Partial validate'),
-  );
-  $form['actions']['partial_numeric_index'] = array(
-    '#type' => 'submit',
-    '#limit_validation_errors' => array(array('test_numeric_index', 0)),
-    '#submit' => array('form_test_limit_validation_errors_form_partial_submit'),
-    '#value' => t('Partial validate (numeric index)'),
-  );
-  $form['actions']['substring'] = array(
-    '#type' => 'submit',
-    '#limit_validation_errors' => array(array('test_substring', 'foo')),
-    '#submit' => array('form_test_limit_validation_errors_form_partial_submit'),
-    '#value' => t('Partial validate (substring)'),
-  );
-  $form['actions']['full'] = array(
-    '#type' => 'submit',
-    '#value' => t('Full validate'),
-  );
-  return $form;
-}
-
-/**
- * Form element validation handler for the 'test' element.
- */
-function form_test_limit_validation_errors_element_validate_test(&$element, &$form_state) {
-  if ($element['#value'] == 'invalid') {
-    form_error($element, $form_state, t('@label element is invalid', array('@label' => $element['#title'])));
-  }
-}
-
-/**
- * Form submit handler for the partial validation submit button.
- */
-function form_test_limit_validation_errors_form_partial_submit($form, $form_state) {
-  // The title has not been validated, thus its value - in case of the test case
-  // an empty string - may not be set.
-  if (!isset($form_state['values']['title']) && isset($form_state['values']['test'])) {
-    drupal_set_message('Only validated values appear in the form values.');
-  }
-}
-
-/**
- * Builds a simple form using the FAPI #pattern proterty.
- *
- * @deprecated Use \Drupal\form_test\validatePattern()
- */
-function form_test_pattern_form($form, &$form_state) {
-  $form['textfield'] = array(
-    '#type' => 'textfield',
-    '#title' => 'One digit followed by lowercase letters',
-    '#pattern' => '[0-9][a-z]+',
-  );
-  $form['tel'] = array(
-    '#type' => 'tel',
-    '#title' => 'Everything except numbers',
-    '#pattern' => '[^\d]*',
-  );
-  $form['password'] = array(
-    '#type' => 'password',
-    '#title' => 'Password',
-    '#pattern' => '[01]+',
-  );
-  $form['url'] = array(
-    '#type' => 'url',
-    '#title' => 'Client side validation',
-    '#decription' => 'Just client side validation, using the #pattern attribute.',
-    '#attributes' => array(
-      'pattern' => '.*foo.*',
-    ),
-    '#pattern' => 'ignored',
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Submit',
-  );
-  return $form;
-}
-
-/**
  * Create a header and options array. Helper function for callbacks.
  */
 function _form_test_tableselect_get_data() {
@@ -385,1080 +89,6 @@ function _form_test_tableselect_get_data() {
 }
 
 /**
- * A multistep form for testing the form storage.
- *
- * It uses two steps for editing a virtual "thing". Any changes to it are saved
- * in the form storage and have to be present during any step. By setting the
- * request parameter "cache" the form can be tested with caching enabled, as
- * it would be the case, if the form would contain some #ajax callbacks.
- *
- * @see form_test_storage_form_submit()
- *
- * @deprecated Use \Drupal\form_test\testStorage()
- */
-function form_test_storage_form($form, &$form_state) {
-  if ($form_state['rebuild']) {
-    $form_state['input'] = array();
-  }
-  // Initialize
-  if (empty($form_state['storage'])) {
-    if (empty($form_state['input'])) {
-      $_SESSION['constructions'] = 0;
-    }
-    // Put the initial thing into the storage
-    $form_state['storage'] = array(
-      'thing' => array(
-        'title' => 'none',
-        'value' => '',
-      ),
-    );
-  }
-  // Count how often the form is constructed.
-  $_SESSION['constructions']++;
-  drupal_set_message("Form constructions: " . $_SESSION['constructions']);
-
-  $form['title'] = array(
-    '#type' => 'textfield',
-    '#title' => 'Title',
-    '#default_value' => $form_state['storage']['thing']['title'],
-    '#required' => TRUE,
-  );
-  $form['value'] = array(
-    '#type' => 'textfield',
-    '#title' => 'Value',
-    '#default_value' => $form_state['storage']['thing']['value'],
-    '#element_validate' => array('form_test_storage_element_validate_value_cached'),
-  );
-  $form['continue_button'] = array(
-    '#type' => 'button',
-    '#value' => 'Reset',
-    // Rebuilds the form without keeping the values.
-  );
-  $form['continue_submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Continue submit',
-    '#submit' => array('form_storage_test_form_continue_submit'),
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Save',
-  );
-
-  if (\Drupal::request()->get('cache')) {
-    // Manually activate caching, so we can test that the storage keeps working
-    // when it's enabled.
-    $form_state['cache'] = TRUE;
-  }
-
-  return $form;
-}
-
-/**
- * Form element validation handler for 'value' element in form_test_storage_form().
- *
- * Tests updating of cached form storage during validation.
- */
-function form_test_storage_element_validate_value_cached($element, &$form_state) {
-  // If caching is enabled and we receive a certain value, change the storage.
-  // This presumes that another submitted form value triggers a validation error
-  // elsewhere in the form. Form API should still update the cached form storage
-  // though.
-  if (\Drupal::request()->get('cache') && $form_state['values']['value'] == 'change_title') {
-    $form_state['storage']['thing']['changed'] = TRUE;
-  }
-}
-
-/**
- * Form submit handler to continue multi-step form.
- */
-function form_storage_test_form_continue_submit($form, &$form_state) {
-  $form_state['storage']['thing']['title'] = $form_state['values']['title'];
-  $form_state['storage']['thing']['value'] = $form_state['values']['value'];
-  $form_state['rebuild'] = TRUE;
-}
-
-/**
- * Form submit handler to finish multi-step form.
- */
-function form_test_storage_form_submit($form, &$form_state) {
-  drupal_set_message("Title: " . String::checkPlain($form_state['values']['title']));
-  drupal_set_message("Form constructions: " . $_SESSION['constructions']);
-  if (isset($form_state['storage']['thing']['changed'])) {
-    drupal_set_message("The thing has been changed.");
-  }
-  $form_state['redirect_route']['route_name'] = '<front>';
-}
-
-/**
- * A form for testing form labels and required marks.
- *
- * @deprecated Use \Drupal\form_test\testLabel()
- */
-function form_label_test_form() {
-  $form['form_checkboxes_test'] = array(
-    '#type' => 'checkboxes',
-    '#title' => t('Checkboxes test'),
-    '#options' => array(
-      'first-checkbox' => t('First checkbox'),
-      'second-checkbox' => t('Second checkbox'),
-      'third-checkbox' => t('Third checkbox'),
-      '0' => t('0'),
-    ),
-  );
-  $form['form_radios_test'] = array(
-    '#type' => 'radios',
-    '#title' => t('Radios test'),
-    '#options' => array(
-      'first-radio' => t('First radio'),
-      'second-radio' => t('Second radio'),
-      'third-radio' => t('Third radio'),
-      '0' => t('0'),
-    ),
-    // Test #field_prefix and #field_suffix placement.
-    '#field_prefix' => '<span id="form-test-radios-field-prefix">' . t('Radios #field_prefix element') . '</span>',
-    '#field_suffix' => '<span id="form-test-radios-field-suffix">' . t('Radios #field_suffix element') . '</span>',
-  );
-  $form['form_checkbox_test'] = array(
-    '#type' => 'checkbox',
-    '#title' => t('Checkbox test'),
-  );
-  $form['form_textfield_test_title_and_required'] = array(
-    '#type' => 'textfield',
-    '#title' => t('Textfield test for required with title'),
-    '#required' => TRUE,
-  );
-  $form['form_textfield_test_no_title_required'] = array(
-    '#type' => 'textfield',
-    // We use an empty title, since not setting #title suppresses the label
-    // and required marker.
-    '#title' => '',
-    '#required' => TRUE,
-  );
-  $form['form_textfield_test_title'] = array(
-    '#type' => 'textfield',
-    '#title' => t('Textfield test for title only'),
-    // Not required.
-    // Test #prefix and #suffix placement.
-    '#prefix' => '<div id="form-test-textfield-title-prefix">' . t('Textfield #prefix element') . '</div>',
-    '#suffix' => '<div id="form-test-textfield-title-suffix">' . t('Textfield #suffix element') . '</div>',
-  );
-  $form['form_textfield_test_title_after'] = array(
-    '#type' => 'textfield',
-    '#title' => t('Textfield test for title after element'),
-    '#title_display' => 'after',
-  );
-  $form['form_textfield_test_title_invisible'] = array(
-    '#type' => 'textfield',
-    '#title' => t('Textfield test for invisible title'),
-    '#title_display' => 'invisible',
-  );
-  // Textfield test for title set not to display.
-  $form['form_textfield_test_title_no_show'] = array(
-    '#type' => 'textfield',
-  );
-  // Checkboxes & radios with title as attribute.
-  $form['form_checkboxes_title_attribute'] = array(
-    '#type' => 'checkboxes',
-    '#title' => 'Checkboxes test',
-    '#title_display' => 'attribute',
-    '#options' => array(
-      'first-checkbox' => 'First checkbox',
-      'second-checkbox' => 'Second checkbox',
-    ),
-    '#required' => TRUE,
-  );
-  $form['form_radios_title_attribute'] = array(
-    '#type' => 'radios',
-    '#title' => 'Radios test',
-    '#title_display' => 'attribute',
-    '#options' => array(
-      'first-radio' => 'First radio',
-      'second-radio' => 'Second radio',
-    ),
-    '#required' => TRUE,
-  );
-
-  return $form;
-}
-
-/**
- * Form builder for form_state_values_clean() test.
- *
- * @deprecated Use \Drupal\form_test\testFormStateClean()
- */
-function form_test_form_state_values_clean_form($form, &$form_state) {
-  // Build an example form containing multiple submit and button elements; not
-  // only on the top-level.
-  $form = array('#tree' => TRUE);
-  $form['foo'] = array('#type' => 'submit', '#value' => t('Submit'));
-  $form['bar'] = array('#type' => 'submit', '#value' => t('Submit'));
-  $form['beer'] = array('#type' => 'value', '#value' => 1000);
-  $form['baz']['foo'] = array('#type' => 'button', '#value' => t('Submit'));
-  $form['baz']['baz'] = array('#type' => 'submit', '#value' => t('Submit'));
-  $form['baz']['beer'] = array('#type' => 'value', '#value' => 2000);
-  return $form;
-}
-
-/**
- * Form submit handler for form_state_values_clean() test form.
- */
-function form_test_form_state_values_clean_form_submit($form, &$form_state) {
-  form_state_values_clean($form_state);
-  // This won't have a proper JSON header, but Drupal doesn't check for that
-  // anyway so this is fine until it's replaced with a JsonResponse.
-  print Json::encode($form_state['values']);
-  exit;
-}
-
-/**
- * Form constructor for the form_state_values_clean() test.
- *
- * @deprecated Use \Drupal\form_test\testFormStateCleanAdvanced()
- */
-function form_test_form_state_values_clean_advanced_form($form, &$form_state) {
-  // Build an example form containing a managed file and a submit form element.
-  $form['image'] = array(
-    '#type' => 'managed_file',
-    '#title' => t('Image'),
-    '#upload_location' => 'public://',
-    '#default_value' => 0,
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => t('Submit'),
-  );
-  return $form;
-}
-
-/**
- * Form submission handler for form_test_form_state_values_clean_advanced_form().
- */
-function form_test_form_state_values_clean_advanced_form_submit($form, &$form_state) {
-  form_state_values_clean($form_state);
-  print t('You WIN!');
-  exit;
-}
-
-/**
- * Builds a form to test #type 'select' validation.
- *
- * @deprecated Use \Drupal\form_test\testSelect()
- */
-function form_test_select($form, &$form_state) {
-  $form['#submit'] = array('_form_test_submit_values_json');
-
-  $base = array(
-    '#type' => 'select',
-    '#options' => array('one' => 'one', 'two' => 'two', 'three' => 'three'),
-  );
-
-  $form['select'] = $base + array(
-    '#title' => '#default_value one',
-    '#default_value' => 'one',
-  );
-  $form['select_required'] = $base + array(
-    '#title' => '#default_value one, #required',
-    '#required' => TRUE,
-    '#default_value' => 'one',
-  );
-  $form['select_optional'] = $base + array(
-    '#title' => '#default_value one, not #required',
-    '#required' => FALSE,
-    '#default_value' => 'one',
-  );
-  $form['empty_value'] = $base + array(
-    '#title' => '#default_value one, #required, #empty_value 0',
-    '#required' => TRUE,
-    '#default_value' => 'one',
-    '#empty_value' => 0,
-  );
-  $form['empty_value_one'] = $base + array(
-    '#title' => '#default_value = #empty_value, #required',
-    '#required' => TRUE,
-    '#default_value' => 'one',
-    '#empty_value' => 'one',
-  );
-
-  $form['no_default'] = $base + array(
-    '#title' => 'No #default_value, #required',
-    '#required' => TRUE,
-  );
-  $form['no_default_optional'] = $base + array(
-    '#title' => 'No #default_value, not #required',
-    '#required' => FALSE,
-    '#description' => 'Should result in "one" because it is not required and there is no #empty_value requested, so default browser behavior of preselecting first option is in effect.',
-  );
-  $form['no_default_optional_empty_value'] = $base + array(
-    '#title' => 'No #default_value, not #required, #empty_value empty string',
-    '#empty_value' => '',
-    '#required' => FALSE,
-    '#description' => 'Should result in an empty string (due to #empty_value) because it is optional.',
-  );
-
-  $form['no_default_empty_option'] = $base + array(
-    '#title' => 'No #default_value, #required, #empty_option',
-    '#required' => TRUE,
-    '#empty_option' => '- Choose -',
-  );
-  $form['no_default_empty_option_optional'] = $base + array(
-    '#title' => 'No #default_value, not #required, #empty_option',
-    '#empty_option' => '- Dismiss -',
-    '#description' => 'Should result in an empty string (default of #empty_value) because it is optional.',
-  );
-
-  $form['no_default_empty_value'] = $base + array(
-    '#title' => 'No #default_value, #required, #empty_value 0',
-    '#required' => TRUE,
-    '#empty_value' => 0,
-    '#description' => 'Should never result in 0.',
-  );
-  $form['no_default_empty_value_one'] = $base + array(
-    '#title' => 'No #default_value, #required, #empty_value one',
-    '#required' => TRUE,
-    '#empty_value' => 'one',
-    '#description' => 'A mistakenly assigned #empty_value contained in #options should not be valid.',
-  );
-  $form['no_default_empty_value_optional'] = $base + array(
-    '#title' => 'No #default_value, not #required, #empty_value 0',
-    '#required' => FALSE,
-    '#empty_value' => 0,
-    '#description' => 'Should result in 0 because it is optional.',
-  );
-
-  $form['multiple'] = $base + array(
-    '#title' => '#multiple, #default_value two',
-    '#default_value' => array('two'),
-    '#multiple' => TRUE,
-  );
-  $form['multiple_no_default'] = $base + array(
-    '#title' => '#multiple, no #default_value',
-    '#multiple' => TRUE,
-  );
-  $form['multiple_no_default_required'] = $base + array(
-    '#title' => '#multiple, #required, no #default_value',
-    '#required' => TRUE,
-    '#multiple' => TRUE,
-  );
-
-  $form['submit'] = array('#type' => 'submit', '#value' => 'Submit');
-  return $form;
-}
-
-/**
- * Builds a form to test select elements when #options is not an array.
- *
- * @deprecated Use \Drupal\form_test\testEmptySelect()
- */
-function form_test_empty_select($form, &$form_state) {
-  $form['empty_select'] = array(
-    '#type' => 'select',
-    '#title' => t('Empty Select'),
-    '#multiple' => FALSE,
-    '#options' => NULL,
-  );
-  return $form;
-}
-
-/**
- * Builds a form to test the language select form element.
- *
- * @deprecated Use \Drupal\form_test\testLanguageSelect()
- */
-function form_test_language_select() {
-  $form['#submit'] = array('_form_test_submit_values_json');
-
-  $form['languages_all'] = array(
-    '#title' => t('Languages: All'),
-    '#type' => 'language_select',
-    '#languages' => LanguageInterface::STATE_ALL,
-    '#default_value' => 'xx',
-  );
-  $form['languages_configurable'] = array(
-    '#title' => t('Languages: Configurable'),
-    '#type' => 'language_select',
-    '#languages' => LanguageInterface::STATE_CONFIGURABLE,
-    '#default_value' => 'en',
-  );
-  $form['languages_locked'] = array(
-    '#title' => t('Languages: Locked'),
-    '#type' => 'language_select',
-    '#languages' => LanguageInterface::STATE_LOCKED,
-  );
-  $form['languages_config_and_locked'] = array(
-    '#title' => t('Languages: Configurable and locked'),
-    '#type' => 'language_select',
-    '#languages' => LanguageInterface::STATE_CONFIGURABLE | LanguageInterface::STATE_LOCKED,
-    '#default_value' => 'dummy_value',
-  );
-  $form['language_custom_options'] = array(
-    '#title' => t('Languages: Custom'),
-    '#type' => 'language_select',
-    '#languages' => LanguageInterface::STATE_CONFIGURABLE | LanguageInterface::STATE_LOCKED,
-    '#options' => array('opt1' => 'First option', 'opt2' => 'Second option', 'opt3' => 'Third option'),
-    '#default_value' => 'opt2',
-  );
-
-  $form['submit'] = array('#type' => 'submit', '#value' => 'Submit');
-  return $form;
-}
-
-/**
- * Builds a form to test #type 'number' and 'range' validation.
- *
- * @param $element
- *   The element type to test. Can be 'number' or 'range'. Defaults to 'number'.
- *
- * @deprecated Use \Drupal\form_test\testNumber()
- *
- * @deprecated Use \Drupal\form_test\testNumberRange()
- */
-function form_test_number($form, &$form_state, $element = 'number') {
-  $base = array(
-    '#type' => $element,
-  );
-
-  $form['integer_no_number'] = $base + array(
-    '#title' => 'Integer test, #no_error',
-    '#default_value' => '#no_number',
-  );
-  $form['integer_no_step'] = $base + array(
-    '#title' => 'Integer test without step',
-    '#default_value' => 5,
-  );
-  $form['integer_no_step_step_error'] = $base + array(
-    '#title' => 'Integer test without step, #step_error',
-    '#default_value' => 4.5,
-  );
-  $form['integer_step'] = $base + array(
-    '#title' => 'Integer test with step',
-    '#default_value' => 5,
-    '#step' => 1,
-  );
-  $form['integer_step_error'] = $base + array(
-    '#title' => 'Integer test, with step, #step_error',
-    '#default_value' => 5,
-    '#step' => 2,
-  );
-  $form['integer_step_min'] = $base + array(
-    '#title' => 'Integer test with min value',
-    '#default_value' => 5,
-    '#min' => 0,
-    '#step' => 1,
-  );
-  $form['integer_step_min_error'] = $base + array(
-    '#title' => 'Integer test with min value, #min_error',
-    '#default_value' => 5,
-    '#min' => 6,
-    '#step' => 1,
-  );
-  $form['integer_step_max'] = $base + array(
-    '#title' => 'Integer test with max value',
-    '#default_value' => 5,
-    '#max' => 6,
-    '#step' => 1,
-  );
-  $form['integer_step_max_error'] = $base + array(
-    '#title' => 'Integer test with max value, #max_error',
-    '#default_value' => 5,
-    '#max' => 4,
-    '#step' => 1,
-  );
-  $form['integer_step_min_border'] = $base + array(
-    '#title' => 'Integer test with min border check',
-    '#default_value' => -1,
-    '#min' => -1,
-    '#step' => 1,
-  );
-  $form['integer_step_max_border'] = $base + array(
-    '#title' => 'Integer test with max border check',
-    '#default_value' => 5,
-    '#max' => 5,
-    '#step' => 1,
-  );
-  $form['integer_step_based_on_min'] = $base + array(
-    '#title' => 'Integer test with step based on min check',
-    '#default_value' => 3,
-    '#min' => -1,
-    '#step' => 2,
-  );
-  $form['integer_step_based_on_min_error'] = $base + array(
-    '#title' => 'Integer test with step based on min check, #step_error',
-    '#default_value' => 4,
-    '#min' => -1,
-    '#step' => 2,
-  );
-  $form['float_small_step'] = $base + array(
-    '#title' => 'Float test with a small step',
-    '#default_value' => 4,
-    '#step' => 0.0000000000001,
-  );
-  $form['float_step_no_error'] = $base + array(
-    '#title' => 'Float test',
-    '#default_value' => 1.2,
-    '#step' => 0.3,
-  );
-  $form['float_step_error'] = $base + array(
-    '#title' => 'Float test, #step_error',
-    '#default_value' => 1.3,
-    '#step' => 0.3,
-  );
-  $form['float_step_hard_no_error'] = $base + array(
-    '#title' => 'Float test hard',
-    '#default_value' => 0.9411764729088,
-    '#step' => 0.00392156863712,
-  );
-  $form['float_step_hard_error'] = $base + array(
-    '#title' => 'Float test hard, #step_error',
-    '#default_value' => 0.9411764,
-    '#step' => 0.00392156863,
-  );
-  $form['float_step_any_no_error'] = $base + array(
-    '#title' => 'Arbitrary float',
-    '#default_value' => 0.839562930284,
-    '#step' => 'aNy',
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Submit',
-  );
-  return $form;
-}
-
-/**
- * Form constructor for testing #type 'range' elements.
- *
- * @see form_test_range_submit()
- *
- * @deprecated Use \Drupal\form_test\testRange()
- */
-function form_test_range($form, &$form_state) {
-  $form['#submit'] = array('_form_test_submit_values_json');
-
-  $form['with_default_value'] = array(
-    '#type' => 'range',
-    '#title' => 'Range with default value',
-    '#min' => 10,
-    '#max' => 20,
-    '#step' => 2,
-    '#default_value' => 18,
-    '#description' => 'The default value is 18.',
-  );
-  $form['float'] = array(
-    '#type' => 'range',
-    '#title' => 'Float',
-    '#min' => 10,
-    '#max' => 11,
-    '#step' => 'any',
-    '#description' => 'Floating point number between 10 and 11.',
-  );
-  $form['integer'] = array(
-    '#type' => 'range',
-    '#title' => 'Integer',
-    '#min' => 2,
-    '#max' => 8,
-    '#step' => 2,
-    '#description' => 'Even integer between 2 and 8.',
-  );
-  $form['offset'] = array(
-    '#type' => 'range',
-    '#title' => 'Offset',
-    '#min' => 2.9,
-    '#max' => 10.9,
-    '#description' => 'Value between 2.9 and 10.9.',
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Submit',
-  );
-  return $form;
-}
-
-/**
- * Form constructor for testing invalid #type 'range' elements.
- *
- * @deprecated Use \Drupal\form_test\testRangeInvalid()
- */
-function form_test_range_invalid($form, &$form_state) {
-  $form['minmax'] = array(
-    '#type' => 'range',
-    '#min' => 10,
-    '#max' => 5,
-    '#title' => 'Invalid range',
-    '#description' => 'Minimum greater than maximum.',
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Submit',
-  );
-  return $form;
-}
-
-/**
- * Form constructor for testing #type 'color' elements.
- *
- * @see form_test_color_submit()
- *
- * @deprecated Use \Drupal\form_test\testColor()
- */
-function form_test_color($form, &$form_state) {
-  $form['#submit'] = array('_form_test_submit_values_json');
-
-  $form['color'] = array(
-    '#type' => 'color',
-    '#title' => 'Color',
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Submit',
-  );
-  return $form;
-}
-
-/**
- * Builds a form to test the placeholder attribute.
- *
- * @deprecated Use \Drupal\form_test\testPlaceholder()
- */
-function form_test_placeholder_test($form, &$form_state) {
-  foreach (array('textfield', 'textarea', 'url', 'password', 'search', 'tel', 'email', 'number') as $type) {
-    $form[$type] = array(
-      '#type' => $type,
-      '#title' => $type,
-      '#placeholder' => 'placeholder-text',
-    );
-  }
-
-  return $form;
-}
-
-/**
- * Form constructor to test expansion of #type checkboxes and radios.
- *
- * @deprecated Use \Drupal\form_test\testCheckboxesRadios()
- */
-function form_test_checkboxes_radios($form, &$form_state, $customize = FALSE) {
-  $form['#submit'] = array('_form_test_submit_values_json');
-
-  // Expand #type checkboxes, setting custom element properties for some but not
-  // all options.
-  $form['checkboxes'] = array(
-    '#type' => 'checkboxes',
-    '#title' => 'Checkboxes',
-    '#options' => array(
-      0 => 'Zero',
-      'foo' => 'Foo',
-      1 => 'One',
-      'bar' => 'Bar',
-      '>' => 'Special Char',
-    ),
-  );
-  if ($customize) {
-    $form['checkboxes'] += array(
-      'foo' => array(
-        '#description' => 'Enable to foo.',
-      ),
-      1 => array(
-        '#weight' => 10,
-      ),
-    );
-  }
-
-  // Expand #type radios, setting custom element properties for some but not
-  // all options.
-  $form['radios'] = array(
-    '#type' => 'radios',
-    '#title' => 'Radios',
-    '#options' => array(
-      0 => 'Zero',
-      'foo' => 'Foo',
-      1 => 'One',
-      'bar' => 'Bar',
-      '>' => 'Special Char',
-    ),
-  );
-  if ($customize) {
-    $form['radios'] += array(
-      'foo' => array(
-        '#description' => 'Enable to foo.',
-      ),
-      1 => array(
-        '#weight' => 10,
-      ),
-    );
-  }
-
-  $form['submit'] = array('#type' => 'submit', '#value' => 'Submit');
-
-  return $form;
-}
-
-/**
- * Form constructor for testing #type 'email' elements.
- *
- * @see form_test_email_submit()
- *
- * @deprecated Use \Drupal\form_test\testEmail()
- */
-function form_test_email($form, &$form_state) {
-  $form['#submit'] = array('_form_test_submit_values_json');
-  $form['email'] = array(
-    '#type' => 'email',
-    '#title' => 'Email address',
-    '#description' => 'An email address.',
-  );
-  $form['email_required'] = array(
-    '#type' => 'email',
-    '#title' => 'Address',
-    '#required' => TRUE,
-    '#description' => 'A required email address field.',
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Submit',
-  );
-  return $form;
-}
-
-/**
- * Form constructor for testing #type 'url' elements.
- *
- * @see form_test_url_submit()
- *
- * @deprecated Use \Drupal\form_test\testUrl()
- */
-function form_test_url($form, &$form_state) {
-  $form['#submit'] = array('_form_test_submit_values_json');
-  $form['url'] = array(
-    '#type' => 'url',
-    '#title' => 'Optional URL',
-    '#description' => 'An optional URL field.',
-  );
-  $form['url_required'] = array(
-    '#type' => 'url',
-    '#title' => 'Required URL',
-    '#description' => 'A required URL field.',
-    '#required' => TRUE,
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Submit',
-  );
-  return $form;
-}
-
-/**
- * Build a form to test disabled elements.
- *
- * @deprecated Use \Drupal\form_test\testDisabledElements()
- */
-function _form_test_disabled_elements($form, &$form_state) {
-  $form['#submit'] = array('_form_test_submit_values_json');
-
-  // Elements that take a simple default value.
-  foreach (array('textfield', 'textarea', 'search', 'tel', 'hidden') as $type) {
-    $form[$type] = array(
-      '#type' => $type,
-      '#title' => $type,
-      '#default_value' => $type,
-      '#test_hijack_value' => 'HIJACK',
-      '#disabled' => TRUE,
-    );
-  }
-
-  // Multiple values option elements.
-  foreach (array('checkboxes', 'select') as $type) {
-    $form[$type . '_multiple'] = array(
-      '#type' => $type,
-      '#title' => $type . ' (multiple)',
-      '#options' => array(
-        'test_1' => 'Test 1',
-        'test_2' => 'Test 2',
-      ),
-      '#multiple' => TRUE,
-      '#default_value' => array('test_2' => 'test_2'),
-      // The keys of #test_hijack_value need to match the #name of the control.
-      // @see FormsTestCase::testDisabledElements()
-      '#test_hijack_value' => $type == 'select' ? array('' => 'test_1') : array('test_1' => 'test_1'),
-      '#disabled' => TRUE,
-    );
-  }
-
-  // Single values option elements.
-  foreach (array('radios', 'select') as $type) {
-    $form[$type . '_single'] = array(
-      '#type' => $type,
-      '#title' => $type . ' (single)',
-      '#options' => array(
-        'test_1' => 'Test 1',
-        'test_2' => 'Test 2',
-      ),
-      '#multiple' => FALSE,
-      '#default_value' => 'test_2',
-      '#test_hijack_value' => 'test_1',
-      '#disabled' => TRUE,
-    );
-  }
-
-  // Checkbox and radio.
-  foreach (array('checkbox', 'radio') as $type) {
-    $form[$type . '_unchecked'] = array(
-      '#type' => $type,
-      '#title' => $type . ' (unchecked)',
-      '#return_value' => 1,
-      '#default_value' => 0,
-      '#test_hijack_value' => 1,
-      '#disabled' => TRUE,
-    );
-    $form[$type . '_checked'] = array(
-      '#type' => $type,
-      '#title' => $type . ' (checked)',
-      '#return_value' => 1,
-      '#default_value' => 1,
-      '#test_hijack_value' => NULL,
-      '#disabled' => TRUE,
-    );
-  }
-
-  // Weight, number, range.
-  foreach (array('weight', 'number', 'range') as $type) {
-    $form[$type] = array(
-      '#type' => $type,
-      '#title' => $type,
-      '#default_value' => 10,
-      '#test_hijack_value' => 5,
-      '#disabled' => TRUE,
-    );
-  }
-
-  // Color.
-  $form['color'] = array(
-    '#type' => 'color',
-    '#title' => 'color',
-    '#default_value' => '#0000ff',
-    '#test_hijack_value' => '#ff0000',
-    '#disabled' => TRUE,
-  );
-
-  // The #disabled state should propagate to children.
-  $form['disabled_container'] = array(
-    '#disabled' => TRUE,
-  );
-  foreach (array('textfield', 'textarea', 'hidden', 'tel', 'url') as $type) {
-    $form['disabled_container']['disabled_container_' . $type] = array(
-      '#type' => $type,
-      '#title' => $type,
-      '#default_value' => $type,
-      '#test_hijack_value' => 'HIJACK',
-    );
-  }
-
-  // Date.
-  $date = new DrupalDateTime('1978-11-01 10:30:00', 'Europe/Berlin');
-  $expected = array('date' => '1978-11-01 10:30:00', 'timezone_type' => 3, 'timezone' => 'Europe/Berlin',);
-  $form['disabled_container']['disabled_container_datetime'] = array(
-    '#type' => 'datetime',
-    '#title' => 'datetime',
-    '#default_value' => $date,
-    '#expected_value' => $expected,
-    '#test_hijack_value' => new DrupalDateTime('1978-12-02 11:30:00', 'Europe/Berlin'),
-    '#date_timezone' => 'Europe/Berlin',
-  );
-
-
-  // Try to hijack the email field with a valid email.
-  $form['disabled_container']['disabled_container_email'] = array(
-    '#type' => 'email',
-    '#title' => 'email',
-    '#default_value' => 'foo@example.com',
-    '#test_hijack_value' => 'bar@example.com',
-  );
-
-  // Try to hijack the URL field with a valid URL.
-  $form['disabled_container']['disabled_container_url'] = array(
-    '#type' => 'url',
-    '#title' => 'url',
-    '#default_value' => 'http://example.com',
-    '#test_hijack_value' => 'http://example.com/foo',
-  );
-
-  // Text format.
-  $form['text_format'] = array(
-    '#type' => 'text_format',
-    '#title' => 'Text format',
-    '#disabled' => TRUE,
-    '#default_value' => 'Text value',
-    '#format' => 'plain_text',
-    '#expected_value' => array(
-      'value' => 'Text value',
-      'format' => 'plain_text',
-    ),
-    '#test_hijack_value' => array(
-      'value' => 'HIJACK',
-      'format' => 'filtered_html',
-    ),
-  );
-
-  // Password fields.
-  $form['password'] = array(
-    '#type' => 'password',
-    '#title' => 'Password',
-    '#disabled' => TRUE,
-  );
-  $form['password_confirm'] = array(
-    '#type' => 'password_confirm',
-    '#title' => 'Password confirm',
-    '#disabled' => TRUE,
-  );
-
-  // Files.
-  $form['file'] = array(
-    '#type' => 'file',
-    '#title' => 'File',
-    '#disabled' => TRUE,
-  );
-  $form['managed_file'] = array(
-    '#type' => 'managed_file',
-    '#title' => 'Managed file',
-    '#disabled' => TRUE,
-  );
-
-  // Buttons.
-  $form['image_button'] = array(
-    '#type' => 'image_button',
-    '#value' => 'Image button',
-    '#disabled' => TRUE,
-  );
-  $form['button'] = array(
-    '#type' => 'button',
-    '#value' => 'Button',
-    '#disabled' => TRUE,
-  );
-  $form['submit_disabled'] = array(
-    '#type' => 'submit',
-    '#value' => 'Submit',
-    '#disabled' => TRUE,
-  );
-
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => t('Submit'),
-  );
-
-  return $form;
-}
-
-/**
- * Form builder for testing preservation of values during a rebuild.
- *
- * @deprecated Use \Drupal\form_test\testRebuildPreservation()
- */
-function form_test_form_rebuild_preserve_values_form($form, &$form_state) {
-  // Start the form with two checkboxes, to test different defaults, and a
-  // textfield, to test more than one element type.
-  $form = array(
-    'checkbox_1_default_off' => array(
-      '#type' => 'checkbox',
-      '#title' => t('This checkbox defaults to unchecked.'),
-      '#default_value' => FALSE,
-    ),
-    'checkbox_1_default_on' => array(
-      '#type' => 'checkbox',
-      '#title' => t('This checkbox defaults to checked.'),
-      '#default_value' => TRUE,
-    ),
-    'text_1' => array(
-      '#type' => 'textfield',
-      '#title' => t('This textfield has a non-empty default value.'),
-      '#default_value' => 'DEFAULT 1',
-    ),
-  );
-  // Provide an 'add more' button that rebuilds the form with an additional two
-  // checkboxes and a textfield. The test is to make sure that the rebuild
-  // triggered by this button preserves the user input values for the initial
-  // elements and initializes the new elements with the correct default values.
-  if (empty($form_state['storage']['add_more'])) {
-    $form['add_more'] = array(
-      '#type' => 'submit',
-      '#value' => 'Add more',
-      '#submit' => array('form_test_form_rebuild_preserve_values_form_add_more'),
-    );
-  }
-  else {
-    $form += array(
-      'checkbox_2_default_off' => array(
-        '#type' => 'checkbox',
-        '#title' => t('This checkbox defaults to unchecked.'),
-        '#default_value' => FALSE,
-      ),
-      'checkbox_2_default_on' => array(
-        '#type' => 'checkbox',
-        '#title' => t('This checkbox defaults to checked.'),
-        '#default_value' => TRUE,
-      ),
-      'text_2' => array(
-        '#type' => 'textfield',
-        '#title' => t('This textfield has a non-empty default value.'),
-        '#default_value' => 'DEFAULT 2',
-      ),
-    );
-  }
-  // A submit button that finishes the form workflow (does not rebuild).
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Submit',
-  );
-  return $form;
-}
-
-/**
- * Button submit handler for form_test_form_rebuild_preserve_values_form().
- */
-function form_test_form_rebuild_preserve_values_form_add_more($form, &$form_state) {
-  // Rebuild, to test preservation of input values.
-  $form_state['storage']['add_more'] = TRUE;
-  $form_state['rebuild'] = TRUE;
-}
-
-/**
- * Form submit handler for form_test_form_rebuild_preserve_values_form().
- */
-function form_test_form_rebuild_preserve_values_form_submit($form, &$form_state) {
-  // Finish the workflow. Do not rebuild.
-  drupal_set_message(t('Form values: %values', array('%values' => var_export($form_state['values'], TRUE))));
-}
-
-/**
- * Form constructor for testing form state persistence.
- *
- * @deprecated Use \Drupal\form_test\testStatePersistence()
- */
-function form_test_state_persist($form, &$form_state) {
-  $form['title'] = array(
-    '#type' => 'textfield',
-    '#title' => 'title',
-    '#default_value' => 'DEFAULT',
-    '#required' => TRUE,
-  );
-  $form_state['value'] = 'State persisted.';
-
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => t('Submit'),
-  );
-  return $form;
-}
-
-/**
- * Submit handler.
- *
- * @see form_test_state_persist()
- */
-function form_test_state_persist_submit($form, &$form_state) {
-  drupal_set_message($form_state['value']);
-  $form_state['rebuild'] = TRUE;
-}
-
-/**
  * Implements hook_form_FORM_ID_alter().
  *
  * @see form_test_state_persist()
@@ -1472,210 +102,6 @@ function form_test_form_form_test_state_persist_alter(&$form, &$form_state) {
 }
 
 /**
- * Form builder to test programmatic form submissions.
- */
-function form_test_programmatic_form($form, &$form_state) {
-  $form['textfield'] = array(
-    '#title' => 'Textfield',
-    '#type' => 'textfield',
-  );
-
-  $form['checkboxes'] = array(
-    '#title' => t('Checkboxes'),
-    '#type' => 'checkboxes',
-    '#options' => array(
-      1 => 'First checkbox',
-      2 => 'Second checkbox',
-    ),
-    // Both checkboxes are selected by default so that we can test the ability
-    // of programmatic form submissions to uncheck them.
-    '#default_value' => array(1, 2),
-  );
-
-  $form['field_to_validate'] = array(
-    '#type' => 'radios',
-    '#title' => 'Field to validate (in the case of limited validation)',
-    '#description' => 'If the form is submitted by clicking the "Submit with limited validation" button, then validation can be limited based on the value of this radio button.',
-    '#options' => array(
-      'all' => 'Validate all fields',
-      'textfield' => 'Validate the "Textfield" field',
-      'field_to_validate' => 'Validate the "Field to validate" field',
-    ),
-    '#default_value' => 'all',
-  );
-
-  $form['field_restricted'] = array(
-    '#type' => 'textfield',
-    '#title' => 'Textfield (no access)',
-    '#access' => FALSE,
-  );
-
-  // The main submit button for the form.
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Submit',
-  );
-  // A secondary submit button that allows validation to be limited based on
-  // the value of the above radio selector.
-  $form['submit_limit_validation'] = array(
-    '#type' => 'submit',
-    '#value' => 'Submit with limited validation',
-    // Use the same submit handler for this button as for the form itself.
-    // (This must be set explicitly or otherwise the form API will ignore the
-    // #limit_validation_errors property.)
-    '#submit' => array('form_test_programmatic_form_submit'),
-  );
-  if (!empty($form_state['input']['field_to_validate']) && $form_state['input']['field_to_validate'] != 'all') {
-    $form['submit_limit_validation']['#limit_validation_errors'] = array(
-      array($form_state['input']['field_to_validate']),
-    );
-  }
-
-  return $form;
-}
-
-/**
- * Form validation handler for programmatic form submissions.
- *
- * To test that the validation handler is correctly executed, the field value is
- * explicitly required here.
- */
-function form_test_programmatic_form_validate($form, &$form_state) {
-  if (empty($form_state['values']['textfield'])) {
-    form_set_error('textfield', $form_state, t('Textfield is required.'));
-  }
-}
-
-/**
- * Form submit handler for programmatic form submissions.
- *
- * To test that the submission handler is correctly executed, we store the
- * submitted values in a place we can access from the caller context.
- */
-function form_test_programmatic_form_submit($form, &$form_state) {
-  $form_state['storage']['programmatic_form_submit'] = $form_state['values'];
-}
-
-/**
- * Form builder to test button click detection.
- *
- * @deprecated Use \Drupal\form_test\testClickedButton()
- */
-function form_test_clicked_button($form, &$form_state, $first, $second, $third) {
-  // A single text field. In IE, when a form has only one non-button input field
-  // and the ENTER key is pressed while that field has focus, the form is
-  // submitted without any information identifying the button responsible for
-  // the submission. In other browsers, the form is submitted as though the
-  // first button were clicked.
-  $form['text'] = array(
-    '#title' => 'Text',
-    '#type' => 'textfield',
-  );
-
-  // Loop through each path argument, addding buttons based on the information
-  // in the argument. For example, if the path is
-  // form-test/clicked-button/s/i/rb, then 3 buttons are added: a 'submit', an
-  // 'image_button', and a 'button' with #access=FALSE. This enables form.test
-  // to test a variety of combinations.
-  $i=0;
-  $args = array($first, $second, $third);
-  foreach ($args as $arg) {
-    $name = 'button' . ++$i;
-    // 's', 'b', or 'i' in the argument define the button type wanted.
-    if (strpos($arg, 's') !== FALSE) {
-      $type = 'submit';
-    }
-    elseif (strpos($arg, 'b') !== FALSE) {
-      $type = 'button';
-    }
-    elseif (strpos($arg, 'i') !== FALSE) {
-      $type = 'image_button';
-    }
-    else {
-      $type = NULL;
-    }
-    if (isset($type)) {
-      $form[$name] = array(
-        '#type' => $type,
-        '#name' => $name,
-      );
-      // Image buttons need a #src; the others need a #value.
-      if ($type == 'image_button') {
-        $form[$name]['#src'] = 'core/misc/druplicon.png';
-      }
-      else {
-        $form[$name]['#value'] = $name;
-      }
-      // 'r' for restricted, so we can test that button click detection code
-      // correctly takes #access security into account.
-      if (strpos($arg, 'r') !== FALSE) {
-        $form[$name]['#access'] = FALSE;
-      }
-    }
-  }
-
-  return $form;
-}
-
-/**
- * Form validation handler for the form_test_clicked_button() form.
- */
-function form_test_clicked_button_validate($form, &$form_state) {
-  if (isset($form_state['triggering_element'])) {
-    drupal_set_message(t('The clicked button is %name.', array('%name' => $form_state['triggering_element']['#name'])));
-  }
-  else {
-    drupal_set_message('There is no clicked button.');
-  }
-}
-
-/**
- * Form submit handler for the form_test_clicked_button() form.
- */
-function form_test_clicked_button_submit($form, &$form_state) {
-  drupal_set_message('Submit handler for form_test_clicked_button executed.');
-}
-
-/**
- * Form builder to detect form redirect.
- *
- * @deprecated Use \Drupal\form_test\testRedirect()
- */
-function form_test_redirect($form, &$form_state) {
-  $form['redirection'] = array(
-    '#type' => 'checkbox',
-    '#title' => t('Use redirection'),
-  );
-  $form['destination'] = array(
-    '#type' => 'textfield',
-    '#title' => t('Redirect destination'),
-    '#states' => array(
-      'visible' => array(
-        ':input[name="redirection"]' => array('checked' => TRUE),
-      ),
-    ),
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => t('Submit'),
-  );
-
-  return $form;
-}
-
-/**
- * Form submit handler to test different redirect behaviors.
- */
-function form_test_redirect_submit(&$form, &$form_state) {
-  if (!empty($form_state['values']['redirection'])) {
-    $form_state['redirect'] = !empty($form_state['values']['destination']) ? $form_state['values']['destination'] : NULL;
-  }
-  else {
-    $form_state['redirect'] = FALSE;
-  }
-}
-
-/**
  * Implements hook_form_FORM_ID_alter() for the registration form.
  */
 function form_test_form_user_register_form_alter(&$form, &$form_state) {
@@ -1693,226 +119,3 @@ function form_test_user_register_form_rebuild($form, &$form_state) {
   drupal_set_message('Form rebuilt.');
   $form_state['rebuild'] = TRUE;
 }
-
-function form_test_checkbox_type_juggling($form, $form_state, $default_value, $return_value) {
-  $form['checkbox'] = array(
-    '#title' => t('Checkbox'),
-    '#type' => 'checkbox',
-    '#return_value' => $return_value,
-    '#default_value' => $default_value,
-  );
-  return $form;
-}
-
-/**
- * Tests checkboxes zero.
- *
- * @deprecated Use \Drupal\form_test\testCheckboxesZero()
- */
-function form_test_checkboxes_zero($form, &$form_state, $json = TRUE) {
-  $form['checkbox_off'] = array(
-    '#title' => t('Checkbox off'),
-    '#type' => 'checkboxes',
-    '#options' => array('foo', 'bar', 'baz'),
-  );
-  $form['checkbox_zero_default'] = array(
-    '#title' => t('Zero default'),
-    '#type' => 'checkboxes',
-    '#options' => array('foo', 'bar', 'baz'),
-    '#default_value' => array(0),
-  );
-  $form['checkbox_string_zero_default'] = array(
-    '#title' => t('Zero default (string)'),
-    '#type' => 'checkboxes',
-    '#options' => array('foo', 'bar', 'baz'),
-    '#default_value' => array('0'),
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Save',
-  );
-  if ($json) {
-    $form['#submit'][] = '_form_test_submit_values_json';
-  }
-  else {
-    $form['#submit'][] = '_form_test_checkboxes_zero_no_redirect';
-  }
-  return $form;
-}
-
-function _form_test_checkboxes_zero_no_redirect($form, &$form_state) {
-  $form_state['redirect'] = FALSE;
-}
-
-/**
- * Builds a form to test the required attribute.
- *
- * @deprecated Use \Drupal\form_test\testRequired()
- */
-function form_test_required_attribute($form, &$form_state) {
-  foreach (array('textfield', 'textarea', 'password') as $type) {
-    $form[$type] = array(
-      '#type' => $type,
-      '#required' => TRUE,
-      '#title' => $type,
-    );
-  }
-
-  return $form;
-}
-
-/**
- * Builds a simple form to test form button classes.
- *
- * @deprecated Use \Drupal\form_test\testButtonClass()
- */
-function form_test_button_class($form, &$form_state) {
-  $form['button'] = array(
-    '#type' => 'button',
-    '#value' => 'test',
-    '#button_type' => 'foo',
-  );
-  $form['delete'] = array(
-    '#type' => 'button',
-    '#value' => 'Delete',
-    '#button_type' => 'danger',
-  );
-  return $form;
-}
-
-/**
- * Builds a simple form to test the #group property on #type 'details'.
- *
- * @deprecated Use \Drupal\form_test\testGroupDetails()
- */
-function form_test_group_details() {
-  $form['details'] = array(
-    '#type' => 'details',
-    '#title' => 'Root element',
-    '#open' => TRUE,
-  );
-  $form['meta'] = array(
-    '#type' => 'details',
-    '#title' => 'Group element',
-    '#open' => TRUE,
-    '#group' => 'details',
-  );
-  $form['meta']['element'] = array(
-    '#type' => 'textfield',
-    '#title' => 'Nest in details element',
-  );
-  return $form;
-}
-
-/**
- * Builds a simple form to test the #group property on #type 'container'.
- *
- * @deprecated Use \Drupal\form_test\testGroupContainer()
- */
-function form_test_group_container() {
-  $form['container'] = array(
-    '#type' => 'container',
-  );
-  $form['meta'] = array(
-    '#type' => 'details',
-    '#title' => 'Group element',
-    '#open' => TRUE,
-    '#group' => 'container',
-  );
-  $form['meta']['element'] = array(
-    '#type' => 'textfield',
-    '#title' => 'Nest in details element',
-  );
-  return $form;
-}
-
-/**
- * Builds a simple form to test the #group property on #type 'fieldset'.
- *
- * @deprecated Use \Drupal\form_test\testGroupFieldset()
- */
-function form_test_group_fieldset() {
-  $form['fieldset'] = array(
-    '#type' => 'fieldset',
-    '#title' => 'Fieldset',
-  );
-  $form['meta'] = array(
-    '#type' => 'container',
-    '#title' => 'Group element',
-    '#group' => 'fieldset',
-  );
-  $form['meta']['element'] = array(
-    '#type' => 'textfield',
-    '#title' => 'Nest in container element',
-  );
-  return $form;
-}
-
-/**
- * Builds a simple form to test the #group property on #type 'vertical_tabs'.
- *
- * @deprecated Use \Drupal\form_test\testGroupVerticalTabs()
- */
-function form_test_group_vertical_tabs() {
-  $form['vertical_tabs'] = array(
-    '#type' => 'vertical_tabs',
-  );
-  $form['meta'] = array(
-    '#type' => 'details',
-    '#title' => 'First group element',
-    '#group' => 'vertical_tabs',
-  );
-  $form['meta']['element'] = array(
-    '#type' => 'textfield',
-    '#title' => 'First nested element in details element',
-  );
-  $form['meta_2'] = array(
-    '#type' => 'details',
-    '#title' => 'Second group element',
-    '#group' => 'vertical_tabs',
-  );
-  $form['meta_2']['element_2'] = array(
-    '#type' => 'textfield',
-    '#title' => 'Second nested element in details element',
-  );
-  return $form;
-}
-
-/**
- * Builds a form which gets the database connection stored in the form state.
- *
- * @deprecated Use \Drupal\form_test\testFormStateDatabase()
- */
-function form_test_form_state_database($form, &$form_state) {
-  $form['text'] = array(
-    '#type' => 'textfield',
-    '#title' => t('Text field'),
-  );
-
-  $form['test_submit'] = array(
-    '#type' => 'submit',
-    '#value' => t('Submit'),
-  );
-
-  $db = Database::getConnection('default');
-  $form_state['storage']['database'] = $db;
-  $form_state['storage']['database_class'] = get_class($db);
-
-  if (isset($form_state['storage']['database_connection_found'])) {
-    $form['database']['#markup'] = 'Database connection found';
-  }
-
-  return $form;
-}
-
-/**
- * Form submit handler for database form_state test.
- */
-function form_test_form_state_database_submit($form, &$form_state) {
-  $form_state['cache'] = TRUE;
-  $form_state['rebuild'] = TRUE;
-
-  if ($form_state['storage']['database'] instanceof $form_state['storage']['database_class']) {
-    $form_state['storage']['database_connection_found'] = TRUE;
-  }
-}
diff --git a/core/modules/system/tests/modules/form_test/form_test.routing.yml b/core/modules/system/tests/modules/form_test/form_test.routing.yml
index 56bd2d5..86d7fc0 100644
--- a/core/modules/system/tests/modules/form_test/form_test.routing.yml
+++ b/core/modules/system/tests/modules/form_test/form_test.routing.yml
@@ -71,7 +71,7 @@ form_test.autocomplete_2:
 form_test.alter_form:
   path: '/form-test/alter'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::alterForm'
+    _form: '\Drupal\form_test\Form\FormTestAlterForm'
     _title: 'Form altering test'
   requirements:
     _access: 'TRUE'
@@ -79,7 +79,7 @@ form_test.alter_form:
 form_test.validate_form:
   path: '/form-test/validate'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::validateForm'
+    _form: '\Drupal\form_test\Form\FormTestValidateForm'
     _title: 'Form validation handlers test'
   requirements:
     _access: 'TRUE'
@@ -87,7 +87,7 @@ form_test.validate_form:
 form_test.validate_required:
   path: '/form-test/validate-required'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::validateRequiredForm'
+    _form: '\Drupal\form_test\Form\FormTestValidateRequiredForm'
     _title: 'Form #required validation'
   requirements:
     _access: 'TRUE'
@@ -95,7 +95,7 @@ form_test.validate_required:
 form_test.validate_required_no_title:
   path: '/form-test/validate-required-no-title'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::validateRequiredFormNoTitle'
+    _form: '\Drupal\form_test\Form\FormTestValidateRequiredNoTitleForm'
     _title: 'Form #required validation without #title'
   requirements:
     _access: 'TRUE'
@@ -103,7 +103,7 @@ form_test.validate_required_no_title:
 form_test.validate_with_error_suppresion:
   path: '/form-test/limit-validation-errors'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::validateFormWithErrorSuppression'
+    _form: '\Drupal\form_test\Form\FormTestLimitValidationErrorsForm'
     _title: 'Form validation with some error suppression'
   requirements:
     _access: 'TRUE'
@@ -111,7 +111,7 @@ form_test.validate_with_error_suppresion:
 form_test.pattern:
   path: '/form-test/pattern'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::validatePattern'
+    _form: '\Drupal\form_test\Form\FormTestPatternForm'
     _title: 'Pattern validation'
   requirements:
     _access: 'TRUE'
@@ -167,7 +167,7 @@ form_test.vertical_tabs:
 form_test.storage:
   path: '/form_test/form-storage'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testStorage'
+    _form: '\Drupal\form_test\Form\FormTestStorageForm'
     _title: 'Form storage test'
   requirements:
     _access: 'TRUE'
@@ -175,7 +175,7 @@ form_test.storage:
 form_test.state_clean:
   path: '/form_test/form-state-values-clean'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testFormStateClean'
+    _form: '\Drupal\form_test\Form\FormTestFormStateValuesCleanForm'
     _title: 'Form state values clearance test'
   requirements:
     _access: 'TRUE'
@@ -183,7 +183,7 @@ form_test.state_clean:
 form_test.state_clean_advanced:
   path: '/form_test/form-state-values-clean-advanced'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testFormStateCleanAdvanced'
+    _form: '\Drupal\form_test\Form\FormTestFormStateValuesCleanAdvancedForm'
     _title: 'Form state values clearance advanced test'
   requirements:
     _access: 'TRUE'
@@ -199,7 +199,7 @@ form_test.checkbox:
 form_test.select:
   path: '/form-test/select'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testSelect'
+    _form: '\Drupal\form_test\Form\FormTestSelectForm'
     _title: 'Select'
   requirements:
     _access: 'TRUE'
@@ -207,7 +207,7 @@ form_test.select:
 form_test.empty_select:
   path: '/form-test/empty-select'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testEmptySelect'
+    _form: '\Drupal\form_test\Form\FormTestEmptySelectForm'
     _title: 'Empty Select Element'
   requirements:
     _access: 'TRUE'
@@ -215,7 +215,7 @@ form_test.empty_select:
 form_test.language_select:
   path: '/form-test/language_select'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testLanguageSelect'
+    _form: '\Drupal\form_test\Form\FormTestLanguageSelectForm'
     _title: 'Language Select'
   requirements:
     _access: 'TRUE'
@@ -223,7 +223,7 @@ form_test.language_select:
 form_test.placeholder:
   path: '/form-test/placeholder-text'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testPlaceholder'
+    _form: '\Drupal\form_test\Form\FormTestPlaceholderForm'
     _title: 'Placeholder'
   requirements:
     _access: 'TRUE'
@@ -231,7 +231,7 @@ form_test.placeholder:
 form_test.number:
   path: '/form-test/number'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testNumber'
+    _form: '\Drupal\form_test\Form\FormTestNumberForm'
     _title: 'Number'
   requirements:
     _access: 'TRUE'
@@ -239,15 +239,16 @@ form_test.number:
 form_test.number_range:
   path: '/form-test/number/range'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testNumberRange'
+    _form: '\Drupal\form_test\Form\FormTestNumberForm'
     _title: 'Range'
+    element: 'range'
   requirements:
     _access: 'TRUE'
 
 form_test.range:
   path: '/form-test/range'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testRange'
+    _form: '\Drupal\form_test\Form\FormTestRangeForm'
     _title: 'Range'
   requirements:
     _access: 'TRUE'
@@ -255,7 +256,7 @@ form_test.range:
 form_test.range_invalid:
   path: '/form-test/range/invalid'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testRangeInvalid'
+    _form: '\Drupal\form_test\Form\FormTestRangeInvalidForm'
     _title: 'Invalid range'
   requirements:
     _access: 'TRUE'
@@ -263,7 +264,7 @@ form_test.range_invalid:
 form_test.color:
   path: '/form-test/color'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testColor'
+    _form: '\Drupal\form_test\Form\FormTestColorForm'
     _title: 'Color'
   requirements:
     _access: 'TRUE'
@@ -271,7 +272,7 @@ form_test.color:
 form_test.checkboxes_radios:
   path: '/form-test/checkboxes-radios/{customize}'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testCheckboxesRadios'
+    _form: '\Drupal\form_test\Form\FormTestCheckboxesRadiosForm'
     _title: 'Checkboxes, Radios'
     customize: FALSE
   requirements:
@@ -280,7 +281,7 @@ form_test.checkboxes_radios:
 form_test.email:
   path: '/form-test/email'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testEmail'
+    _form: '\Drupal\form_test\Form\FormTestEmailForm'
     _title: 'Email fields'
   requirements:
     _access: 'TRUE'
@@ -288,7 +289,7 @@ form_test.email:
 form_test.url:
   path: '/form-test/url'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testUrl'
+    _form: '\Drupal\form_test\Form\FormTestUrlForm'
     _title: 'URL'
   requirements:
     _access: 'TRUE'
@@ -296,7 +297,7 @@ form_test.url:
 form_test.disabled_elements:
   path: '/form-test/disabled-elements'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testDisabledElements'
+    _form: '\Drupal\form_test\Form\FormTestDisabledElementsForm'
     _title: 'Form test'
   requirements:
     _access: 'TRUE'
@@ -312,7 +313,7 @@ form_test.input_forgery:
 form_test.rebuild_preservation:
   path: '/form-test/form-rebuild-preserve-values'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testRebuildPreservation'
+    _form: '\Drupal\form_test\Form\FormTestRebuildPreserveValuesForm'
     _title: 'Form values preservation during rebuild test'
   requirements:
     _access: 'TRUE'
@@ -320,7 +321,7 @@ form_test.rebuild_preservation:
 form_test.redirect:
   path: '/form-test/redirect'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testRedirect'
+    _form: '\Drupal\form_test\Form\FormTestRedirectForm'
     _title: 'Redirect test'
   requirements:
     _access: 'TRUE'
@@ -328,7 +329,7 @@ form_test.redirect:
 form_test.label:
   path: '/form_test/form-labels'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testLabel'
+    _form: '\Drupal\form_test\Form\FormTestLabelForm'
     _title: 'Form label test'
   requirements:
     _access: 'TRUE'
@@ -336,7 +337,7 @@ form_test.label:
 form_test.state_persistence:
   path: '/form-test/state-persist'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testStatePersistence'
+    _form: '\Drupal\form_test\Form\FormTestStatePersistForm'
     _title: 'Form state persistence without storage'
   requirements:
     _access: 'TRUE'
@@ -344,7 +345,7 @@ form_test.state_persistence:
 form_test.clicked_button:
   path: '/form-test/clicked-button/{first}/{second}/{third}'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testClickedButton'
+    _form: '\Drupal\form_test\Form\FormTestClickedButtonForm'
     _title: 'Clicked button test'
     first: NULL
     second: NULL
@@ -355,7 +356,7 @@ form_test.clicked_button:
 form_test.checkboxes_zero:
   path: '/form-test/checkboxes-zero/{json}'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testCheckboxesZero'
+    _form: '\Drupal\form_test\Form\FormTestCheckboxesZeroForm'
     _title: 'FAPI test involving checkboxes and zero'
     json: TRUE
   requirements:
@@ -364,7 +365,7 @@ form_test.checkboxes_zero:
 form_test.required:
   path: '/form-test/required-attribute'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testRequired'
+    _form: '\Drupal\form_test\Form\FormTestRequiredAttributeForm'
     _title: 'Required'
   requirements:
     _access: 'TRUE'
@@ -372,7 +373,7 @@ form_test.required:
 form_test.button_class:
   path: '/form-test/button-class'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testButtonClass'
+    _form: '\Drupal\form_test\Form\FormTestButtonClassForm'
     _title: 'Button class testing'
   requirements:
     _access: 'TRUE'
@@ -380,7 +381,7 @@ form_test.button_class:
 form_test.group_details:
   path: '/form-test/group-details'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testGroupDetails'
+    _form: '\Drupal\form_test\Form\FormTestGroupDetailsForm'
     _title: 'Group details testing'
   requirements:
     _access: 'TRUE'
@@ -388,7 +389,7 @@ form_test.group_details:
 form_test.group_container:
   path: '/form-test/group-container'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testGroupContainer'
+    _form: '\Drupal\form_test\Form\FormTestGroupContainerForm'
     _title: 'Group container testing'
   requirements:
     _access: 'TRUE'
@@ -396,7 +397,7 @@ form_test.group_container:
 form_test.group_fieldset:
   path: '/form-test/group-fieldset'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testGroupFieldset'
+    _form: '\Drupal\form_test\Form\FormTestGroupFieldsetForm'
     _title: 'Group fieldset testing'
   requirements:
     _access: 'TRUE'
@@ -404,7 +405,7 @@ form_test.group_fieldset:
 form_test.group_vertical_tabs:
   path: '/form-test/group-vertical-tabs'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testGroupVerticalTabs'
+    _form: '\Drupal\form_test\Form\FormTestGroupVerticalTabsForm'
     _title: 'Group vertical tabs testing'
   requirements:
     _access: 'TRUE'
@@ -412,7 +413,7 @@ form_test.group_vertical_tabs:
 form_test.form_state_database:
   path: '/form-test/form_state-database'
   defaults:
-    _content: '\Drupal\form_test\Form\FormTestForm::testFormStateDatabase'
+    _form: '\Drupal\form_test\Form\FormTestFormStateDatabaseForm'
     _title: 'Form state with a database connection'
   requirements:
     _access: 'TRUE'
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestAlterForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestAlterForm.php
new file mode 100644
index 0000000..3052d76
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestAlterForm.php
@@ -0,0 +1,40 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestAlterForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Form builder for testing hook_form_alter() and hook_form_FORM_ID_alter().
+ */
+class FormTestAlterForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_alter_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    // Elements can be added as needed for future testing needs, but for now,
+    // we're only testing alter hooks that do not require any elements added by
+    // this function.
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestButtonClassForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestButtonClassForm.php
new file mode 100644
index 0000000..1110120
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestButtonClassForm.php
@@ -0,0 +1,47 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestButtonClassForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a simple form to test form button classes.
+ */
+class FormTestButtonClassForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_button_class';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['button'] = array(
+      '#type' => 'button',
+      '#value' => 'test',
+      '#button_type' => 'foo',
+    );
+    $form['delete'] = array(
+      '#type' => 'button',
+      '#value' => 'Delete',
+      '#button_type' => 'danger',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxForm.php
index 09c825d..1ca9a16 100644
--- a/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxForm.php
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxForm.php
@@ -91,10 +91,7 @@ public function buildForm(array $form, array &$form_state) {
    * {@inheritdoc}
    */
   public function submitForm(array &$form, array &$form_state) {
-    $response = new JsonResponse($form_state['values']);
-    // @todo remove once converted to new routing system.
-    $response->send();
-    exit;
+    $form_state['response'] = new JsonResponse($form_state['values']);
   }
 
 }
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxTypeJugglingForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxTypeJugglingForm.php
new file mode 100644
index 0000000..64a2206
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxTypeJugglingForm.php
@@ -0,0 +1,43 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestCheckboxTypeJugglingForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a form to test return values for checkboxes.
+ */
+class FormTestCheckboxTypeJugglingForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_checkbox_type_juggling';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state, $default_value = NULL, $return_value = NULL) {
+    $form['checkbox'] = array(
+      '#title' => t('Checkbox'),
+      '#type' => 'checkbox',
+      '#return_value' => $return_value,
+      '#default_value' => $default_value,
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxesRadiosForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxesRadiosForm.php
new file mode 100644
index 0000000..4b84cf1
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxesRadiosForm.php
@@ -0,0 +1,89 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestCheckboxesRadiosForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Symfony\Component\HttpFoundation\JsonResponse;
+
+/**
+ * Form constructor to test expansion of #type checkboxes and radios.
+ */
+class FormTestCheckboxesRadiosForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_checkboxes_radios';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state, $customize = FALSE) {
+    // Expand #type checkboxes, setting custom element properties for some but not
+    // all options.
+    $form['checkboxes'] = array(
+      '#type' => 'checkboxes',
+      '#title' => 'Checkboxes',
+      '#options' => array(
+        0 => 'Zero',
+        'foo' => 'Foo',
+        1 => 'One',
+        'bar' => 'Bar',
+        '>' => 'Special Char',
+      ),
+    );
+    if ($customize) {
+      $form['checkboxes'] += array(
+        'foo' => array(
+          '#description' => 'Enable to foo.',
+        ),
+        1 => array(
+          '#weight' => 10,
+        ),
+      );
+    }
+
+    // Expand #type radios, setting custom element properties for some but not
+    // all options.
+    $form['radios'] = array(
+      '#type' => 'radios',
+      '#title' => 'Radios',
+      '#options' => array(
+        0 => 'Zero',
+        'foo' => 'Foo',
+        1 => 'One',
+        'bar' => 'Bar',
+        '>' => 'Special Char',
+      ),
+    );
+    if ($customize) {
+      $form['radios'] += array(
+        'foo' => array(
+          '#description' => 'Enable to foo.',
+        ),
+        1 => array(
+          '#weight' => 10,
+        ),
+      );
+    }
+
+    $form['submit'] = array('#type' => 'submit', '#value' => 'Submit');
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $form_state['response'] = new JsonResponse($form_state['values']);
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxesZeroForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxesZeroForm.php
new file mode 100644
index 0000000..08356ad
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestCheckboxesZeroForm.php
@@ -0,0 +1,66 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestCheckboxesZeroForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Symfony\Component\HttpFoundation\JsonResponse;
+
+/**
+ * Tests checkboxes zero.
+ */
+class FormTestCheckboxesZeroForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_checkboxes_zero';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state, $json = TRUE) {
+    $form_state['json'] = $json;
+    $form['checkbox_off'] = array(
+      '#title' => t('Checkbox off'),
+      '#type' => 'checkboxes',
+      '#options' => array('foo', 'bar', 'baz'),
+    );
+    $form['checkbox_zero_default'] = array(
+      '#title' => t('Zero default'),
+      '#type' => 'checkboxes',
+      '#options' => array('foo', 'bar', 'baz'),
+      '#default_value' => array(0),
+    );
+    $form['checkbox_string_zero_default'] = array(
+      '#title' => t('Zero default (string)'),
+      '#type' => 'checkboxes',
+      '#options' => array('foo', 'bar', 'baz'),
+      '#default_value' => array('0'),
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Save',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    if (!empty($form_state['json'])) {
+      $form_state['response'] = new JsonResponse($form_state['values']);
+    }
+    else {
+      $form_state['redirect'] = FALSE;
+    }
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestClickedButtonForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestClickedButtonForm.php
new file mode 100644
index 0000000..c8464c1
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestClickedButtonForm.php
@@ -0,0 +1,102 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestClickedButtonForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Form builder to test button click detection.
+ */
+class FormTestClickedButtonForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_clicked_button';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state, $first = NULL, $second = NULL, $third = NULL) {
+    // A single text field. In IE, when a form has only one non-button input field
+    // and the ENTER key is pressed while that field has focus, the form is
+    // submitted without any information identifying the button responsible for
+    // the submission. In other browsers, the form is submitted as though the
+    // first button were clicked.
+    $form['text'] = array(
+      '#title' => 'Text',
+      '#type' => 'textfield',
+    );
+
+    // Loop through each path argument, adding buttons based on the information
+    // in the argument. For example, if the path is
+    // form-test/clicked-button/s/i/rb, then 3 buttons are added: a 'submit', an
+    // 'image_button', and a 'button' with #access=FALSE. This enables form.test
+    // to test a variety of combinations.
+    $i = 0;
+    $args = array($first, $second, $third);
+    foreach ($args as $arg) {
+      $name = 'button' . ++$i;
+      // 's', 'b', or 'i' in the argument define the button type wanted.
+      if (strpos($arg, 's') !== FALSE) {
+        $type = 'submit';
+      }
+      elseif (strpos($arg, 'b') !== FALSE) {
+        $type = 'button';
+      }
+      elseif (strpos($arg, 'i') !== FALSE) {
+        $type = 'image_button';
+      }
+      else {
+        $type = NULL;
+      }
+      if (isset($type)) {
+        $form[$name] = array(
+          '#type' => $type,
+          '#name' => $name,
+        );
+        // Image buttons need a #src; the others need a #value.
+        if ($type == 'image_button') {
+          $form[$name]['#src'] = 'core/misc/druplicon.png';
+        }
+        else {
+          $form[$name]['#value'] = $name;
+        }
+        // 'r' for restricted, so we can test that button click detection code
+        // correctly takes #access security into account.
+        if (strpos($arg, 'r') !== FALSE) {
+          $form[$name]['#access'] = FALSE;
+        }
+      }
+    }
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, array &$form_state) {
+    if (isset($form_state['triggering_element'])) {
+      drupal_set_message(t('The clicked button is %name.', array('%name' => $form_state['triggering_element']['#name'])));
+    }
+    else {
+      drupal_set_message('There is no clicked button.');
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    drupal_set_message('Submit handler for form_test_clicked_button executed.');
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestColorForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestColorForm.php
new file mode 100644
index 0000000..0856026
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestColorForm.php
@@ -0,0 +1,47 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestColorForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Symfony\Component\HttpFoundation\JsonResponse;
+
+/**
+ * Form constructor for testing #type 'color' elements.
+ */
+class FormTestColorForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_color';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['color'] = array(
+      '#type' => 'color',
+      '#title' => 'Color',
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Submit',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $form_state['response'] = new JsonResponse($form_state['values']);
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestDisabledElementsForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestDisabledElementsForm.php
new file mode 100644
index 0000000..9f4e168
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestDisabledElementsForm.php
@@ -0,0 +1,230 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestDisabledElementsForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Datetime\DrupalDateTime;
+use Drupal\Core\Form\FormBase;
+use Symfony\Component\HttpFoundation\JsonResponse;
+
+/**
+ * Builds a form to test disabled elements.
+ */
+class FormTestDisabledElementsForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return '_form_test_disabled_elements';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    // Elements that take a simple default value.
+    foreach (array('textfield', 'textarea', 'search', 'tel', 'hidden') as $type) {
+      $form[$type] = array(
+        '#type' => $type,
+        '#title' => $type,
+        '#default_value' => $type,
+        '#test_hijack_value' => 'HIJACK',
+        '#disabled' => TRUE,
+      );
+    }
+
+    // Multiple values option elements.
+    foreach (array('checkboxes', 'select') as $type) {
+      $form[$type . '_multiple'] = array(
+        '#type' => $type,
+        '#title' => $type . ' (multiple)',
+        '#options' => array(
+          'test_1' => 'Test 1',
+          'test_2' => 'Test 2',
+        ),
+        '#multiple' => TRUE,
+        '#default_value' => array('test_2' => 'test_2'),
+        // The keys of #test_hijack_value need to match the #name of the control.
+        // @see FormsTestCase::testDisabledElements()
+        '#test_hijack_value' => $type == 'select' ? array('' => 'test_1') : array('test_1' => 'test_1'),
+        '#disabled' => TRUE,
+      );
+    }
+
+    // Single values option elements.
+    foreach (array('radios', 'select') as $type) {
+      $form[$type . '_single'] = array(
+        '#type' => $type,
+        '#title' => $type . ' (single)',
+        '#options' => array(
+          'test_1' => 'Test 1',
+          'test_2' => 'Test 2',
+        ),
+        '#multiple' => FALSE,
+        '#default_value' => 'test_2',
+        '#test_hijack_value' => 'test_1',
+        '#disabled' => TRUE,
+      );
+    }
+
+    // Checkbox and radio.
+    foreach (array('checkbox', 'radio') as $type) {
+      $form[$type . '_unchecked'] = array(
+        '#type' => $type,
+        '#title' => $type . ' (unchecked)',
+        '#return_value' => 1,
+        '#default_value' => 0,
+        '#test_hijack_value' => 1,
+        '#disabled' => TRUE,
+      );
+      $form[$type . '_checked'] = array(
+        '#type' => $type,
+        '#title' => $type . ' (checked)',
+        '#return_value' => 1,
+        '#default_value' => 1,
+        '#test_hijack_value' => NULL,
+        '#disabled' => TRUE,
+      );
+    }
+
+    // Weight, number, range.
+    foreach (array('weight', 'number', 'range') as $type) {
+      $form[$type] = array(
+        '#type' => $type,
+        '#title' => $type,
+        '#default_value' => 10,
+        '#test_hijack_value' => 5,
+        '#disabled' => TRUE,
+      );
+    }
+
+    // Color.
+    $form['color'] = array(
+      '#type' => 'color',
+      '#title' => 'color',
+      '#default_value' => '#0000ff',
+      '#test_hijack_value' => '#ff0000',
+      '#disabled' => TRUE,
+    );
+
+    // The #disabled state should propagate to children.
+    $form['disabled_container'] = array(
+      '#disabled' => TRUE,
+    );
+    foreach (array('textfield', 'textarea', 'hidden', 'tel', 'url') as $type) {
+      $form['disabled_container']['disabled_container_' . $type] = array(
+        '#type' => $type,
+        '#title' => $type,
+        '#default_value' => $type,
+        '#test_hijack_value' => 'HIJACK',
+      );
+    }
+
+    // Date.
+    $date = new DrupalDateTime('1978-11-01 10:30:00', 'Europe/Berlin');
+    $expected = array('date' => '1978-11-01 10:30:00', 'timezone_type' => 3, 'timezone' => 'Europe/Berlin',);
+    $form['disabled_container']['disabled_container_datetime'] = array(
+      '#type' => 'datetime',
+      '#title' => 'datetime',
+      '#default_value' => $date,
+      '#expected_value' => $expected,
+      '#test_hijack_value' => new DrupalDateTime('1978-12-02 11:30:00', 'Europe/Berlin'),
+      '#date_timezone' => 'Europe/Berlin',
+    );
+
+
+    // Try to hijack the email field with a valid email.
+    $form['disabled_container']['disabled_container_email'] = array(
+      '#type' => 'email',
+      '#title' => 'email',
+      '#default_value' => 'foo@example.com',
+      '#test_hijack_value' => 'bar@example.com',
+    );
+
+    // Try to hijack the URL field with a valid URL.
+    $form['disabled_container']['disabled_container_url'] = array(
+      '#type' => 'url',
+      '#title' => 'url',
+      '#default_value' => 'http://example.com',
+      '#test_hijack_value' => 'http://example.com/foo',
+    );
+
+    // Text format.
+    $form['text_format'] = array(
+      '#type' => 'text_format',
+      '#title' => 'Text format',
+      '#disabled' => TRUE,
+      '#default_value' => 'Text value',
+      '#format' => 'plain_text',
+      '#expected_value' => array(
+        'value' => 'Text value',
+        'format' => 'plain_text',
+      ),
+      '#test_hijack_value' => array(
+        'value' => 'HIJACK',
+        'format' => 'filtered_html',
+      ),
+    );
+
+    // Password fields.
+    $form['password'] = array(
+      '#type' => 'password',
+      '#title' => 'Password',
+      '#disabled' => TRUE,
+    );
+    $form['password_confirm'] = array(
+      '#type' => 'password_confirm',
+      '#title' => 'Password confirm',
+      '#disabled' => TRUE,
+    );
+
+    // Files.
+    $form['file'] = array(
+      '#type' => 'file',
+      '#title' => 'File',
+      '#disabled' => TRUE,
+    );
+    $form['managed_file'] = array(
+      '#type' => 'managed_file',
+      '#title' => 'Managed file',
+      '#disabled' => TRUE,
+    );
+
+    // Buttons.
+    $form['image_button'] = array(
+      '#type' => 'image_button',
+      '#value' => 'Image button',
+      '#disabled' => TRUE,
+    );
+    $form['button'] = array(
+      '#type' => 'button',
+      '#value' => 'Button',
+      '#disabled' => TRUE,
+    );
+    $form['submit_disabled'] = array(
+      '#type' => 'submit',
+      '#value' => 'Submit',
+      '#disabled' => TRUE,
+    );
+
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => t('Submit'),
+    );
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $form_state['response'] = new JsonResponse($form_state['values']);
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestEmailForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestEmailForm.php
new file mode 100644
index 0000000..f46ec64
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestEmailForm.php
@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestEmailForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Symfony\Component\HttpFoundation\JsonResponse;
+
+/**
+ * Form constructor for testing #type 'email' elements.
+ */
+class FormTestEmailForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_email';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['email'] = array(
+      '#type' => 'email',
+      '#title' => 'Email address',
+      '#description' => 'An email address.',
+    );
+    $form['email_required'] = array(
+      '#type' => 'email',
+      '#title' => 'Address',
+      '#required' => TRUE,
+      '#description' => 'A required email address field.',
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Submit',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $form_state['response'] = new JsonResponse($form_state['values']);
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestEmptySelectForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestEmptySelectForm.php
new file mode 100644
index 0000000..1434370
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestEmptySelectForm.php
@@ -0,0 +1,43 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestEmptySelectForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a form to test select elements when #options is not an array.
+ */
+class FormTestEmptySelectForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_empty_select';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['empty_select'] = array(
+      '#type' => 'select',
+      '#title' => t('Empty Select'),
+      '#multiple' => FALSE,
+      '#options' => NULL,
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestForm.php
deleted file mode 100644
index c777732..0000000
--- a/core/modules/system/tests/modules/form_test/src/Form/FormTestForm.php
+++ /dev/null
@@ -1,330 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\form_test\Form\FormTestForm.
- */
-
-namespace Drupal\form_test\Form;
-
-/**
- * Temporary form controller for form_test module.
- */
-class FormTestForm {
-
-  /**
-   * Wraps form_test_alter_form().
-   *
-   * @todo Remove form_test_alter_form().
-   */
-  public function alterForm() {
-    return \Drupal::formBuilder()->getForm('form_test_alter_form');
-  }
-
-  /**
-   * Wraps form_test_validate_form().
-   *
-   * @todo Remove form_test_validate_form().
-   */
-  public function validateForm() {
-    return \Drupal::formBuilder()->getForm('form_test_validate_form');
-  }
-
-  /**
-   * Wraps form_test_validate_required_form().
-   *
-   * @todo Remove form_test_validate_required_form().
-   */
-  public function validateRequiredForm() {
-    return \Drupal::formBuilder()->getForm('form_test_validate_required_form');
-  }
-
-  /**
-   * Wraps form_test_validate_required_form_no_title().
-   *
-   * @todo Remove form_test_validate_required_form_no_title().
-   */
-  public function validateRequiredFormNoTitle() {
-    return \Drupal::formBuilder()->getForm('form_test_validate_required_form_no_title');
-  }
-
-  /**
-   * Wraps form_test_limit_validation_errors_form().
-   *
-   * @todo Remove form_test_limit_validation_errors_form().
-   */
-  public function validateFormWithErrorSuppression() {
-    return \Drupal::formBuilder()->getForm('form_test_limit_validation_errors_form');
-  }
-
-  /**
-   * Wraps form_test_pattern_form().
-   *
-   * @todo Remove form_test_pattern_form().
-   */
-  public function validatePattern() {
-    return \Drupal::formBuilder()->getForm('form_test_pattern_form');
-  }
-
-  /**
-   * Wraps form_test_storage_form().
-   *
-   * @todo Remove form_test_storage_form().
-   */
-  public function testStorage() {
-    return \Drupal::formBuilder()->getForm('form_test_storage_form');
-  }
-
-  /**
-   * Wraps form_test_form_state_values_clean_form().
-   *
-   * @todo Remove form_test_form_state_values_clean_form().
-   */
-  public function testFormStateClean() {
-    return \Drupal::formBuilder()->getForm('form_test_form_state_values_clean_form');
-  }
-
-  /**
-   * Wraps form_test_form_state_values_clean_advanced_form().
-   *
-   * @todo Remove form_test_form_state_values_clean_advanced_form().
-   */
-  public function testFormStateCleanAdvanced() {
-    return \Drupal::formBuilder()->getForm('form_test_form_state_values_clean_advanced_form');
-  }
-
-  /**
-   * Wraps form_test_select().
-   *
-   * @todo Remove form_test_select().
-   */
-  public function testSelect() {
-    return \Drupal::formBuilder()->getForm('form_test_select');
-  }
-
-  /**
-   * Wraps form_test_empty_select().
-   *
-   * @todo Remove form_test_empty_select().
-   */
-  public function testEmptySelect() {
-    return \Drupal::formBuilder()->getForm('form_test_empty_select');
-  }
-
-  /**
-   * Wraps form_test_language_select().
-   *
-   * @todo Remove form_test_language_select().
-   */
-  public function testLanguageSelect() {
-    return \Drupal::formBuilder()->getForm('form_test_language_select');
-  }
-
-  /**
-   * Wraps form_test_placeholder_test().
-   *
-   * @todo Remove form_test_placeholder_test().
-   */
-  public function testPlaceholder() {
-    return \Drupal::formBuilder()->getForm('form_test_placeholder_test');
-  }
-
-  /**
-   * Wraps form_test_number().
-   *
-   * @todo Remove form_test_number().
-   */
-  public function testNumber() {
-    return \Drupal::formBuilder()->getForm('form_test_number');
-  }
-
-  /**
-   * Wraps form_test_number().
-   *
-   * @todo Remove form_test_number().
-   */
-  public function testNumberRange() {
-    return \Drupal::formBuilder()->getForm('form_test_number', 'range');
-  }
-
-  /**
-   * Wraps form_test_range().
-   *
-   * @todo Remove form_test_range().
-   */
-  public function testRange() {
-    return \Drupal::formBuilder()->getForm('form_test_range');
-  }
-
-  /**
-   * Wraps form_test_range_invalid().
-   *
-   * @todo Remove form_test_range_invalid().
-   */
-  public function testRangeInvalid() {
-    return \Drupal::formBuilder()->getForm('form_test_range_invalid');
-  }
-
-  /**
-   * Wraps form_test_color().
-   *
-   * @todo Remove form_test_color().
-   */
-  public function testColor() {
-    return \Drupal::formBuilder()->getForm('form_test_color');
-  }
-
-  /**
-   * Wraps form_test_checkboxes_radios().
-   *
-   * @todo Remove form_test_checkboxes_radios().
-   */
-  public function testCheckboxesRadios($customize) {
-    return \Drupal::formBuilder()->getForm('form_test_checkboxes_radios', $customize);
-  }
-
-  /**
-   * Wraps form_test_email().
-   *
-   * @todo Remove form_test_email().
-   */
-  public function testEmail() {
-    return \Drupal::formBuilder()->getForm('form_test_email');
-  }
-
-  /**
-   * Wraps form_test_url().
-   *
-   * @todo Remove form_test_url().
-   */
-  public function testUrl() {
-    return \Drupal::formBuilder()->getForm('form_test_url');
-  }
-
-  /**
-   * Wraps _form_test_disabled_elements().
-   *
-   * @todo Remove _form_test_disabled_elements().
-   */
-  public function testDisabledElements() {
-    return \Drupal::formBuilder()->getForm('_form_test_disabled_elements');
-  }
-
-  /**
-   * Wraps form_test_form_rebuild_preserve_values_form().
-   *
-   * @todo Remove form_test_form_rebuild_preserve_values_form().
-   */
-  public function testRebuildPreservation() {
-    return \Drupal::formBuilder()->getForm('form_test_form_rebuild_preserve_values_form');
-  }
-
-  /**
-   * Wraps form_test_redirect().
-   *
-   * @todo Remove form_test_redirect().
-   */
-  public function testRedirect() {
-    return \Drupal::formBuilder()->getForm('form_test_redirect');
-  }
-
-  /**
-   * Wraps form_label_test_form().
-   *
-   * @todo Remove form_label_test_form().
-   */
-  public function testLabel() {
-    return \Drupal::formBuilder()->getForm('form_label_test_form');
-  }
-
-  /**
-   * Wraps form_test_state_persist().
-   *
-   * @todo Remove form_test_state_persist().
-   */
-  public function testStatePersistence() {
-    return \Drupal::formBuilder()->getForm('form_test_state_persist');
-  }
-
-  /**
-   * Wraps form_test_clicked_button().
-   *
-   * @todo Remove form_test_clicked_button().
-   */
-  public function testClickedButton($first, $second, $third) {
-    return \Drupal::formBuilder()->getForm('form_test_clicked_button', $first, $second, $third);
-  }
-
-  /**
-   * Wraps form_test_checkboxes_zero().
-   *
-   * @todo Remove form_test_checkboxes_zero().
-   */
-  public function testCheckboxesZero($json) {
-    return \Drupal::formBuilder()->getForm('form_test_checkboxes_zero', $json);
-  }
-
-  /**
-   * Wraps form_test_required_attribute().
-   *
-   * @todo Remove form_test_required_attribute().
-   */
-  public function testRequired() {
-    return \Drupal::formBuilder()->getForm('form_test_required_attribute');
-  }
-
-  /**
-   * Wraps form_test_button_class().
-   *
-   * @todo Remove form_test_button_class().
-   */
-  public function testButtonClass() {
-    return \Drupal::formBuilder()->getForm('form_test_button_class');
-  }
-
-  /**
-   * Wraps form_test_group_details().
-   *
-   * @todo Remove form_test_group_details().
-   */
-  public function testGroupDetails() {
-    return \Drupal::formBuilder()->getForm('form_test_group_details');
-  }
-
-  /**
-   * Wraps form_test_group_container().
-   *
-   * @todo Remove form_test_group_container().
-   */
-  public function testGroupContainer() {
-    return \Drupal::formBuilder()->getForm('form_test_group_container');
-  }
-
-  /**
-   * Wraps form_test_group_fieldset().
-   *
-   * @todo Remove form_test_group_fieldset().
-   */
-  public function testGroupFieldset() {
-    return \Drupal::formBuilder()->getForm('form_test_group_fieldset');
-  }
-
-  /**
-   * Wraps form_test_group_vertical_tabs().
-   *
-   * @todo Remove form_test_group_vertical_tabs().
-   */
-  public function testGroupVerticalTabs() {
-    return \Drupal::formBuilder()->getForm('form_test_group_vertical_tabs');
-  }
-
-  /**
-   * Wraps form_test_form_state_database().
-   *
-   * @todo Remove form_test_form_state_database().
-   */
-  public function testFormStateDatabase() {
-    return \Drupal::formBuilder()->getForm('form_test_form_state_database');
-  }
-
-}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestFormStateDatabaseForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestFormStateDatabaseForm.php
new file mode 100644
index 0000000..f570e2b
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestFormStateDatabaseForm.php
@@ -0,0 +1,62 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestFormStateDatabaseForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Database\Database;
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a form which gets the database connection stored in the form state.
+ */
+class FormTestFormStateDatabaseForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_form_state_database';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['text'] = array(
+      '#type' => 'textfield',
+      '#title' => t('Text field'),
+    );
+
+    $form['test_submit'] = array(
+      '#type' => 'submit',
+      '#value' => t('Submit'),
+    );
+
+    $db = Database::getConnection('default');
+    $form_state['storage']['database'] = $db;
+    $form_state['storage']['database_class'] = get_class($db);
+
+    if (isset($form_state['storage']['database_connection_found'])) {
+      $form['database']['#markup'] = 'Database connection found';
+    }
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $form_state['cache'] = TRUE;
+    $form_state['rebuild'] = TRUE;
+
+    if ($form_state['storage']['database'] instanceof $form_state['storage']['database_class']) {
+      $form_state['storage']['database_connection_found'] = TRUE;
+    }
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestFormStateValuesCleanAdvancedForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestFormStateValuesCleanAdvancedForm.php
new file mode 100644
index 0000000..879d7b3
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestFormStateValuesCleanAdvancedForm.php
@@ -0,0 +1,51 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestFormStateValuesCleanAdvancedForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Form builder for form_state_values_clean() test.
+ */
+class FormTestFormStateValuesCleanAdvancedForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_form_state_values_clean_advanced_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    // Build an example form containing a managed file and a submit form element.
+    $form['image'] = array(
+      '#type' => 'managed_file',
+      '#title' => t('Image'),
+      '#upload_location' => 'public://',
+      '#default_value' => 0,
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => t('Submit'),
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    form_state_values_clean($form_state);
+    print t('You WIN!');
+    exit;
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestFormStateValuesCleanForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestFormStateValuesCleanForm.php
new file mode 100644
index 0000000..5c258d4
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestFormStateValuesCleanForm.php
@@ -0,0 +1,52 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestFormStateValuesCleanForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Component\Serialization\Json;
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Form builder for form_state_values_clean() test.
+ */
+class FormTestFormStateValuesCleanForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_form_state_values_clean_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    // Build an example form containing multiple submit and button elements; not
+    // only on the top-level.
+    $form = array('#tree' => TRUE);
+    $form['foo'] = array('#type' => 'submit', '#value' => t('Submit'));
+    $form['bar'] = array('#type' => 'submit', '#value' => t('Submit'));
+    $form['beer'] = array('#type' => 'value', '#value' => 1000);
+    $form['baz']['foo'] = array('#type' => 'button', '#value' => t('Submit'));
+    $form['baz']['baz'] = array('#type' => 'submit', '#value' => t('Submit'));
+    $form['baz']['beer'] = array('#type' => 'value', '#value' => 2000);
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    form_state_values_clean($form_state);
+    // This won't have a proper JSON header, but Drupal doesn't check for that
+    // anyway so this is fine until it's replaced with a JsonResponse.
+    print Json::encode($form_state['values']);
+    exit;
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupContainerForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupContainerForm.php
new file mode 100644
index 0000000..72c672e
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupContainerForm.php
@@ -0,0 +1,50 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestGroupContainerForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a simple form to test the #group property on #type 'container'.
+ */
+class FormTestGroupContainerForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_group_container';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['container'] = array(
+      '#type' => 'container',
+    );
+    $form['meta'] = array(
+      '#type' => 'details',
+      '#title' => 'Group element',
+      '#open' => TRUE,
+      '#group' => 'container',
+    );
+    $form['meta']['element'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Nest in details element',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupDetailsForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupDetailsForm.php
new file mode 100644
index 0000000..fe94c13
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupDetailsForm.php
@@ -0,0 +1,52 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestGroupDetailsForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a simple form to test the #group property on #type 'details'.
+ */
+class FormTestGroupDetailsForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_group_details';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['details'] = array(
+      '#type' => 'details',
+      '#title' => 'Root element',
+      '#open' => TRUE,
+    );
+    $form['meta'] = array(
+      '#type' => 'details',
+      '#title' => 'Group element',
+      '#open' => TRUE,
+      '#group' => 'details',
+    );
+    $form['meta']['element'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Nest in details element',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupFieldsetForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupFieldsetForm.php
new file mode 100644
index 0000000..5d4a7a8
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupFieldsetForm.php
@@ -0,0 +1,50 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestGroupFieldsetForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a simple form to test the #group property on #type 'fieldset'.
+ */
+class FormTestGroupFieldsetForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_group_fieldset';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['fieldset'] = array(
+      '#type' => 'fieldset',
+      '#title' => 'Fieldset',
+    );
+    $form['meta'] = array(
+      '#type' => 'container',
+      '#title' => 'Group element',
+      '#group' => 'fieldset',
+    );
+    $form['meta']['element'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Nest in container element',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupVerticalTabsForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupVerticalTabsForm.php
new file mode 100644
index 0000000..b92e22d
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestGroupVerticalTabsForm.php
@@ -0,0 +1,58 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestGroupVerticalTabsForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a simple form to test the #group property on #type 'vertical_tabs'.
+ */
+class FormTestGroupVerticalTabsForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_group_vertical_tabs';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['vertical_tabs'] = array(
+      '#type' => 'vertical_tabs',
+    );
+    $form['meta'] = array(
+      '#type' => 'details',
+      '#title' => 'First group element',
+      '#group' => 'vertical_tabs',
+    );
+    $form['meta']['element'] = array(
+      '#type' => 'textfield',
+      '#title' => 'First nested element in details element',
+    );
+    $form['meta_2'] = array(
+      '#type' => 'details',
+      '#title' => 'Second group element',
+      '#group' => 'vertical_tabs',
+    );
+    $form['meta_2']['element_2'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Second nested element in details element',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestLabelForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestLabelForm.php
new file mode 100644
index 0000000..2e24091
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestLabelForm.php
@@ -0,0 +1,120 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestLabelForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * A form for testing form labels and required marks.
+ */
+class FormTestLabelForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_label_test_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['form_checkboxes_test'] = array(
+      '#type' => 'checkboxes',
+      '#title' => t('Checkboxes test'),
+      '#options' => array(
+        'first-checkbox' => t('First checkbox'),
+        'second-checkbox' => t('Second checkbox'),
+        'third-checkbox' => t('Third checkbox'),
+        '0' => t('0'),
+      ),
+    );
+    $form['form_radios_test'] = array(
+      '#type' => 'radios',
+      '#title' => t('Radios test'),
+      '#options' => array(
+        'first-radio' => t('First radio'),
+        'second-radio' => t('Second radio'),
+        'third-radio' => t('Third radio'),
+        '0' => t('0'),
+      ),
+      // Test #field_prefix and #field_suffix placement.
+      '#field_prefix' => '<span id="form-test-radios-field-prefix">' . t('Radios #field_prefix element') . '</span>',
+      '#field_suffix' => '<span id="form-test-radios-field-suffix">' . t('Radios #field_suffix element') . '</span>',
+    );
+    $form['form_checkbox_test'] = array(
+      '#type' => 'checkbox',
+      '#title' => t('Checkbox test'),
+    );
+    $form['form_textfield_test_title_and_required'] = array(
+      '#type' => 'textfield',
+      '#title' => t('Textfield test for required with title'),
+      '#required' => TRUE,
+    );
+    $form['form_textfield_test_no_title_required'] = array(
+      '#type' => 'textfield',
+      // We use an empty title, since not setting #title suppresses the label
+      // and required marker.
+      '#title' => '',
+      '#required' => TRUE,
+    );
+    $form['form_textfield_test_title'] = array(
+      '#type' => 'textfield',
+      '#title' => t('Textfield test for title only'),
+      // Not required.
+      // Test #prefix and #suffix placement.
+      '#prefix' => '<div id="form-test-textfield-title-prefix">' . t('Textfield #prefix element') . '</div>',
+      '#suffix' => '<div id="form-test-textfield-title-suffix">' . t('Textfield #suffix element') . '</div>',
+    );
+    $form['form_textfield_test_title_after'] = array(
+      '#type' => 'textfield',
+      '#title' => t('Textfield test for title after element'),
+      '#title_display' => 'after',
+    );
+    $form['form_textfield_test_title_invisible'] = array(
+      '#type' => 'textfield',
+      '#title' => t('Textfield test for invisible title'),
+      '#title_display' => 'invisible',
+    );
+    // Textfield test for title set not to display.
+    $form['form_textfield_test_title_no_show'] = array(
+      '#type' => 'textfield',
+    );
+    // Checkboxes & radios with title as attribute.
+    $form['form_checkboxes_title_attribute'] = array(
+      '#type' => 'checkboxes',
+      '#title' => 'Checkboxes test',
+      '#title_display' => 'attribute',
+      '#options' => array(
+        'first-checkbox' => 'First checkbox',
+        'second-checkbox' => 'Second checkbox',
+      ),
+      '#required' => TRUE,
+    );
+    $form['form_radios_title_attribute'] = array(
+      '#type' => 'radios',
+      '#title' => 'Radios test',
+      '#title_display' => 'attribute',
+      '#options' => array(
+        'first-radio' => 'First radio',
+        'second-radio' => 'Second radio',
+      ),
+      '#required' => TRUE,
+    );
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestLanguageSelectForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestLanguageSelectForm.php
new file mode 100644
index 0000000..711b369
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestLanguageSelectForm.php
@@ -0,0 +1,72 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestLanguageSelectForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Drupal\Core\Language\LanguageInterface;
+use Symfony\Component\HttpFoundation\JsonResponse;
+
+/**
+ * Builds a form to test the language select form element.
+ */
+class FormTestLanguageSelectForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_language_select';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['languages_all'] = array(
+      '#title' => t('Languages: All'),
+      '#type' => 'language_select',
+      '#languages' => LanguageInterface::STATE_ALL,
+      '#default_value' => 'xx',
+    );
+    $form['languages_configurable'] = array(
+      '#title' => t('Languages: Configurable'),
+      '#type' => 'language_select',
+      '#languages' => LanguageInterface::STATE_CONFIGURABLE,
+      '#default_value' => 'en',
+    );
+    $form['languages_locked'] = array(
+      '#title' => t('Languages: Locked'),
+      '#type' => 'language_select',
+      '#languages' => LanguageInterface::STATE_LOCKED,
+    );
+    $form['languages_config_and_locked'] = array(
+      '#title' => t('Languages: Configurable and locked'),
+      '#type' => 'language_select',
+      '#languages' => LanguageInterface::STATE_CONFIGURABLE | LanguageInterface::STATE_LOCKED,
+      '#default_value' => 'dummy_value',
+    );
+    $form['language_custom_options'] = array(
+      '#title' => t('Languages: Custom'),
+      '#type' => 'language_select',
+      '#languages' => LanguageInterface::STATE_CONFIGURABLE | LanguageInterface::STATE_LOCKED,
+      '#options' => array('opt1' => 'First option', 'opt2' => 'Second option', 'opt3' => 'Third option'),
+      '#default_value' => 'opt2',
+    );
+
+    $form['submit'] = array('#type' => 'submit', '#value' => 'Submit');
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $form_state['response'] = new JsonResponse($form_state['values']);
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestLimitValidationErrorsForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestLimitValidationErrorsForm.php
new file mode 100644
index 0000000..6fdbb25
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestLimitValidationErrorsForm.php
@@ -0,0 +1,113 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestLimitValidationErrorsForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a simple form with a button triggering partial validation.
+ */
+class FormTestLimitValidationErrorsForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_limit_validation_errors_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['title'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Title',
+      '#required' => TRUE,
+    );
+
+    $form['test'] = array(
+      '#title' => 'Test',
+      '#type' => 'textfield',
+      '#element_validate' => array(array($this, 'elementValidateLimitValidationErrors')),
+    );
+    $form['test_numeric_index'] = array(
+      '#tree' => TRUE,
+    );
+    $form['test_numeric_index'][0] = array(
+      '#title' => 'Test (numeric index)',
+      '#type' => 'textfield',
+      '#element_validate' => array(array($this, 'elementValidateLimitValidationErrors')),
+    );
+
+    $form['test_substring'] = array(
+      '#tree' => TRUE,
+    );
+    $form['test_substring']['foo'] = array(
+      '#title' => 'Test (substring) foo',
+      '#type' => 'textfield',
+      '#element_validate' => array(array($this, 'elementValidateLimitValidationErrors')),
+    );
+    $form['test_substring']['foobar'] = array(
+      '#title' => 'Test (substring) foobar',
+      '#type' => 'textfield',
+      '#element_validate' => array(array($this, 'elementValidateLimitValidationErrors')),
+    );
+
+    $form['actions']['partial'] = array(
+      '#type' => 'submit',
+      '#limit_validation_errors' => array(array('test')),
+      '#submit' => array(array($this, 'partialSubmitForm')),
+      '#value' => t('Partial validate'),
+    );
+    $form['actions']['partial_numeric_index'] = array(
+      '#type' => 'submit',
+      '#limit_validation_errors' => array(array('test_numeric_index', 0)),
+      '#submit' => array(array($this, 'partialSubmitForm')),
+      '#value' => t('Partial validate (numeric index)'),
+    );
+    $form['actions']['substring'] = array(
+      '#type' => 'submit',
+      '#limit_validation_errors' => array(array('test_substring', 'foo')),
+      '#submit' => array(array($this, 'partialSubmitForm')),
+      '#value' => t('Partial validate (substring)'),
+    );
+    $form['actions']['full'] = array(
+      '#type' => 'submit',
+      '#value' => t('Full validate'),
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function elementValidateLimitValidationErrors($element, &$form_state) {
+    if ($element['#value'] == 'invalid') {
+      form_error($element, $form_state, t('@label element is invalid', array('@label' => $element['#title'])));
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function partialSubmitForm(array &$form, array &$form_state) {
+    // The title has not been validated, thus its value - in case of the test case
+    // an empty string - may not be set.
+    if (!isset($form_state['values']['title']) && isset($form_state['values']['test'])) {
+      drupal_set_message('Only validated values appear in the form values.');
+    }
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestNumberForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestNumberForm.php
new file mode 100644
index 0000000..7c313fc
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestNumberForm.php
@@ -0,0 +1,145 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestNumberForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a form to test #type 'number' and 'range' validation.
+ */
+class FormTestNumberForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_number';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state, $element = 'number') {
+    $base = array(
+      '#type' => $element,
+    );
+
+    $form['integer_no_number'] = $base + array(
+      '#title' => 'Integer test, #no_error',
+      '#default_value' => '#no_number',
+    );
+    $form['integer_no_step'] = $base + array(
+      '#title' => 'Integer test without step',
+      '#default_value' => 5,
+    );
+    $form['integer_no_step_step_error'] = $base + array(
+      '#title' => 'Integer test without step, #step_error',
+      '#default_value' => 4.5,
+    );
+    $form['integer_step'] = $base + array(
+      '#title' => 'Integer test with step',
+      '#default_value' => 5,
+      '#step' => 1,
+    );
+    $form['integer_step_error'] = $base + array(
+      '#title' => 'Integer test, with step, #step_error',
+      '#default_value' => 5,
+      '#step' => 2,
+    );
+    $form['integer_step_min'] = $base + array(
+      '#title' => 'Integer test with min value',
+      '#default_value' => 5,
+      '#min' => 0,
+      '#step' => 1,
+    );
+    $form['integer_step_min_error'] = $base + array(
+      '#title' => 'Integer test with min value, #min_error',
+      '#default_value' => 5,
+      '#min' => 6,
+      '#step' => 1,
+    );
+    $form['integer_step_max'] = $base + array(
+      '#title' => 'Integer test with max value',
+      '#default_value' => 5,
+      '#max' => 6,
+      '#step' => 1,
+    );
+    $form['integer_step_max_error'] = $base + array(
+      '#title' => 'Integer test with max value, #max_error',
+      '#default_value' => 5,
+      '#max' => 4,
+      '#step' => 1,
+    );
+    $form['integer_step_min_border'] = $base + array(
+      '#title' => 'Integer test with min border check',
+      '#default_value' => -1,
+      '#min' => -1,
+      '#step' => 1,
+    );
+    $form['integer_step_max_border'] = $base + array(
+      '#title' => 'Integer test with max border check',
+      '#default_value' => 5,
+      '#max' => 5,
+      '#step' => 1,
+    );
+    $form['integer_step_based_on_min'] = $base + array(
+      '#title' => 'Integer test with step based on min check',
+      '#default_value' => 3,
+      '#min' => -1,
+      '#step' => 2,
+    );
+    $form['integer_step_based_on_min_error'] = $base + array(
+      '#title' => 'Integer test with step based on min check, #step_error',
+      '#default_value' => 4,
+      '#min' => -1,
+      '#step' => 2,
+    );
+    $form['float_small_step'] = $base + array(
+      '#title' => 'Float test with a small step',
+      '#default_value' => 4,
+      '#step' => 0.0000000000001,
+    );
+    $form['float_step_no_error'] = $base + array(
+      '#title' => 'Float test',
+      '#default_value' => 1.2,
+      '#step' => 0.3,
+    );
+    $form['float_step_error'] = $base + array(
+      '#title' => 'Float test, #step_error',
+      '#default_value' => 1.3,
+      '#step' => 0.3,
+    );
+    $form['float_step_hard_no_error'] = $base + array(
+      '#title' => 'Float test hard',
+      '#default_value' => 0.9411764729088,
+      '#step' => 0.00392156863712,
+    );
+    $form['float_step_hard_error'] = $base + array(
+      '#title' => 'Float test hard, #step_error',
+      '#default_value' => 0.9411764,
+      '#step' => 0.00392156863,
+    );
+    $form['float_step_any_no_error'] = $base + array(
+      '#title' => 'Arbitrary float',
+      '#default_value' => 0.839562930284,
+      '#step' => 'aNy',
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Submit',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestPatternForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestPatternForm.php
new file mode 100644
index 0000000..7df5f7a
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestPatternForm.php
@@ -0,0 +1,65 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestPatternForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a simple form using the FAPI #pattern proterty.
+ */
+class FormTestPatternForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_pattern_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['textfield'] = array(
+      '#type' => 'textfield',
+      '#title' => 'One digit followed by lowercase letters',
+      '#pattern' => '[0-9][a-z]+',
+    );
+    $form['tel'] = array(
+      '#type' => 'tel',
+      '#title' => 'Everything except numbers',
+      '#pattern' => '[^\d]*',
+    );
+    $form['password'] = array(
+      '#type' => 'password',
+      '#title' => 'Password',
+      '#pattern' => '[01]+',
+    );
+    $form['url'] = array(
+      '#type' => 'url',
+      '#title' => 'Client side validation',
+      '#decription' => 'Just client side validation, using the #pattern attribute.',
+      '#attributes' => array(
+        'pattern' => '.*foo.*',
+      ),
+      '#pattern' => 'ignored',
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Submit',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestPlaceholderForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestPlaceholderForm.php
new file mode 100644
index 0000000..f11d9d4
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestPlaceholderForm.php
@@ -0,0 +1,45 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestPlaceholderForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a form to test the placeholder attribute.
+ */
+class FormTestPlaceholderForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_placeholder_test';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    foreach (array('textfield', 'textarea', 'url', 'password', 'search', 'tel', 'email', 'number') as $type) {
+      $form[$type] = array(
+        '#type' => $type,
+        '#title' => $type,
+        '#placeholder' => 'placeholder-text',
+      );
+    }
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestProgrammaticForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestProgrammaticForm.php
new file mode 100644
index 0000000..a44b8c4
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestProgrammaticForm.php
@@ -0,0 +1,103 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestProgrammaticForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Form builder to test programmatic form submissions.
+ */
+class FormTestProgrammaticForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_programmatic_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['textfield'] = array(
+      '#title' => 'Textfield',
+      '#type' => 'textfield',
+    );
+
+    $form['checkboxes'] = array(
+      '#title' => t('Checkboxes'),
+      '#type' => 'checkboxes',
+      '#options' => array(
+        1 => 'First checkbox',
+        2 => 'Second checkbox',
+      ),
+      // Both checkboxes are selected by default so that we can test the ability
+      // of programmatic form submissions to uncheck them.
+      '#default_value' => array(1, 2),
+    );
+
+    $form['field_to_validate'] = array(
+      '#type' => 'radios',
+      '#title' => 'Field to validate (in the case of limited validation)',
+      '#description' => 'If the form is submitted by clicking the "Submit with limited validation" button, then validation can be limited based on the value of this radio button.',
+      '#options' => array(
+        'all' => 'Validate all fields',
+        'textfield' => 'Validate the "Textfield" field',
+        'field_to_validate' => 'Validate the "Field to validate" field',
+      ),
+      '#default_value' => 'all',
+    );
+
+    $form['field_restricted'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Textfield (no access)',
+      '#access' => FALSE,
+    );
+
+    // The main submit button for the form.
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Submit',
+    );
+    // A secondary submit button that allows validation to be limited based on
+    // the value of the above radio selector.
+    $form['submit_limit_validation'] = array(
+      '#type' => 'submit',
+      '#value' => 'Submit with limited validation',
+      // Use the same submit handler for this button as for the form itself.
+      // (This must be set explicitly or otherwise the form API will ignore the
+      // #limit_validation_errors property.)
+      '#submit' => array(array($this, 'submitForm')),
+    );
+    if (!empty($form_state['input']['field_to_validate']) && $form_state['input']['field_to_validate'] != 'all') {
+      $form['submit_limit_validation']['#limit_validation_errors'] = array(
+        array($form_state['input']['field_to_validate']),
+      );
+    }
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, array &$form_state) {
+    if (empty($form_state['values']['textfield'])) {
+      form_set_error('textfield', $form_state, t('Textfield is required.'));
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $form_state['storage']['programmatic_form_submit'] = $form_state['values'];
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestRangeForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestRangeForm.php
new file mode 100644
index 0000000..fff5126
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestRangeForm.php
@@ -0,0 +1,75 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestRangeForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Symfony\Component\HttpFoundation\JsonResponse;
+
+/**
+ * Form constructor for testing #type 'range' elements.
+ */
+class FormTestRangeForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_range';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['with_default_value'] = array(
+      '#type' => 'range',
+      '#title' => 'Range with default value',
+      '#min' => 10,
+      '#max' => 20,
+      '#step' => 2,
+      '#default_value' => 18,
+      '#description' => 'The default value is 18.',
+    );
+    $form['float'] = array(
+      '#type' => 'range',
+      '#title' => 'Float',
+      '#min' => 10,
+      '#max' => 11,
+      '#step' => 'any',
+      '#description' => 'Floating point number between 10 and 11.',
+    );
+    $form['integer'] = array(
+      '#type' => 'range',
+      '#title' => 'Integer',
+      '#min' => 2,
+      '#max' => 8,
+      '#step' => 2,
+      '#description' => 'Even integer between 2 and 8.',
+    );
+    $form['offset'] = array(
+      '#type' => 'range',
+      '#title' => 'Offset',
+      '#min' => 2.9,
+      '#max' => 10.9,
+      '#description' => 'Value between 2.9 and 10.9.',
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Submit',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $form_state['response'] = new JsonResponse($form_state['values']);
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestRangeInvalidForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestRangeInvalidForm.php
new file mode 100644
index 0000000..7b685a7
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestRangeInvalidForm.php
@@ -0,0 +1,48 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestRangeInvalidForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Form constructor for testing invalid #type 'range' elements.
+ */
+class FormTestRangeInvalidForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_range_invalid';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['minmax'] = array(
+      '#type' => 'range',
+      '#min' => 10,
+      '#max' => 5,
+      '#title' => 'Invalid range',
+      '#description' => 'Minimum greater than maximum.',
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Submit',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestRebuildPreserveValuesForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestRebuildPreserveValuesForm.php
new file mode 100644
index 0000000..e1ecced
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestRebuildPreserveValuesForm.php
@@ -0,0 +1,102 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestRebuildPreserveValuesForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Form builder for testing preservation of values during a rebuild.
+ */
+class FormTestRebuildPreserveValuesForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_form_rebuild_preserve_values_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    // Start the form with two checkboxes, to test different defaults, and a
+    // textfield, to test more than one element type.
+    $form = array(
+      'checkbox_1_default_off' => array(
+        '#type' => 'checkbox',
+        '#title' => t('This checkbox defaults to unchecked.'),
+        '#default_value' => FALSE,
+      ),
+      'checkbox_1_default_on' => array(
+        '#type' => 'checkbox',
+        '#title' => t('This checkbox defaults to checked.'),
+        '#default_value' => TRUE,
+      ),
+      'text_1' => array(
+        '#type' => 'textfield',
+        '#title' => t('This textfield has a non-empty default value.'),
+        '#default_value' => 'DEFAULT 1',
+      ),
+    );
+    // Provide an 'add more' button that rebuilds the form with an additional two
+    // checkboxes and a textfield. The test is to make sure that the rebuild
+    // triggered by this button preserves the user input values for the initial
+    // elements and initializes the new elements with the correct default values.
+    if (empty($form_state['storage']['add_more'])) {
+      $form['add_more'] = array(
+        '#type' => 'submit',
+        '#value' => 'Add more',
+        '#submit' => array(array($this, 'addMoreSubmitForm')),
+      );
+    }
+    else {
+      $form += array(
+        'checkbox_2_default_off' => array(
+          '#type' => 'checkbox',
+          '#title' => t('This checkbox defaults to unchecked.'),
+          '#default_value' => FALSE,
+        ),
+        'checkbox_2_default_on' => array(
+          '#type' => 'checkbox',
+          '#title' => t('This checkbox defaults to checked.'),
+          '#default_value' => TRUE,
+        ),
+        'text_2' => array(
+          '#type' => 'textfield',
+          '#title' => t('This textfield has a non-empty default value.'),
+          '#default_value' => 'DEFAULT 2',
+        ),
+      );
+    }
+    // A submit button that finishes the form workflow (does not rebuild).
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Submit',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addMoreSubmitForm(array &$form, array &$form_state) {
+    // Rebuild, to test preservation of input values.
+    $form_state['storage']['add_more'] = TRUE;
+    $form_state['rebuild'] = TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    // Finish the workflow. Do not rebuild.
+    drupal_set_message(t('Form values: %values', array('%values' => var_export($form_state['values'], TRUE))));
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestRedirectForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestRedirectForm.php
new file mode 100644
index 0000000..98219d9
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestRedirectForm.php
@@ -0,0 +1,61 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestRedirectForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Form builder to detect form redirect.
+ */
+class FormTestRedirectForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_redirect';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['redirection'] = array(
+      '#type' => 'checkbox',
+      '#title' => t('Use redirection'),
+    );
+    $form['destination'] = array(
+      '#type' => 'textfield',
+      '#title' => t('Redirect destination'),
+      '#states' => array(
+        'visible' => array(
+          ':input[name="redirection"]' => array('checked' => TRUE),
+        ),
+      ),
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => t('Submit'),
+    );
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    if (!empty($form_state['values']['redirection'])) {
+      $form_state['redirect'] = !empty($form_state['values']['destination']) ? $form_state['values']['destination'] : NULL;
+    }
+    else {
+      $form_state['redirect'] = FALSE;
+    }
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestRequiredAttributeForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestRequiredAttributeForm.php
new file mode 100644
index 0000000..380d1c9
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestRequiredAttributeForm.php
@@ -0,0 +1,45 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestRequiredAttributeForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Builds a form to test the required attribute.
+ */
+class FormTestRequiredAttributeForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_required_attribute';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    foreach (array('textfield', 'textarea', 'password') as $type) {
+      $form[$type] = array(
+        '#type' => $type,
+        '#required' => TRUE,
+        '#title' => $type,
+      );
+    }
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestSelectForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestSelectForm.php
new file mode 100644
index 0000000..5227ae4
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestSelectForm.php
@@ -0,0 +1,133 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestSelectForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Symfony\Component\HttpFoundation\JsonResponse;
+
+/**
+ * Builds a form to test #type 'select' validation.
+ */
+class FormTestSelectForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_select';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $base = array(
+      '#type' => 'select',
+      '#options' => array('one' => 'one', 'two' => 'two', 'three' => 'three'),
+    );
+
+    $form['select'] = $base + array(
+      '#title' => '#default_value one',
+      '#default_value' => 'one',
+    );
+    $form['select_required'] = $base + array(
+      '#title' => '#default_value one, #required',
+      '#required' => TRUE,
+      '#default_value' => 'one',
+    );
+    $form['select_optional'] = $base + array(
+      '#title' => '#default_value one, not #required',
+      '#required' => FALSE,
+      '#default_value' => 'one',
+    );
+    $form['empty_value'] = $base + array(
+      '#title' => '#default_value one, #required, #empty_value 0',
+      '#required' => TRUE,
+      '#default_value' => 'one',
+      '#empty_value' => 0,
+    );
+    $form['empty_value_one'] = $base + array(
+      '#title' => '#default_value = #empty_value, #required',
+      '#required' => TRUE,
+      '#default_value' => 'one',
+      '#empty_value' => 'one',
+    );
+
+    $form['no_default'] = $base + array(
+      '#title' => 'No #default_value, #required',
+      '#required' => TRUE,
+    );
+    $form['no_default_optional'] = $base + array(
+      '#title' => 'No #default_value, not #required',
+      '#required' => FALSE,
+      '#description' => 'Should result in "one" because it is not required and there is no #empty_value requested, so default browser behavior of preselecting first option is in effect.',
+    );
+    $form['no_default_optional_empty_value'] = $base + array(
+      '#title' => 'No #default_value, not #required, #empty_value empty string',
+      '#empty_value' => '',
+      '#required' => FALSE,
+      '#description' => 'Should result in an empty string (due to #empty_value) because it is optional.',
+    );
+
+    $form['no_default_empty_option'] = $base + array(
+      '#title' => 'No #default_value, #required, #empty_option',
+      '#required' => TRUE,
+      '#empty_option' => '- Choose -',
+    );
+    $form['no_default_empty_option_optional'] = $base + array(
+      '#title' => 'No #default_value, not #required, #empty_option',
+      '#empty_option' => '- Dismiss -',
+      '#description' => 'Should result in an empty string (default of #empty_value) because it is optional.',
+    );
+
+    $form['no_default_empty_value'] = $base + array(
+      '#title' => 'No #default_value, #required, #empty_value 0',
+      '#required' => TRUE,
+      '#empty_value' => 0,
+      '#description' => 'Should never result in 0.',
+    );
+    $form['no_default_empty_value_one'] = $base + array(
+      '#title' => 'No #default_value, #required, #empty_value one',
+      '#required' => TRUE,
+      '#empty_value' => 'one',
+      '#description' => 'A mistakenly assigned #empty_value contained in #options should not be valid.',
+    );
+    $form['no_default_empty_value_optional'] = $base + array(
+      '#title' => 'No #default_value, not #required, #empty_value 0',
+      '#required' => FALSE,
+      '#empty_value' => 0,
+      '#description' => 'Should result in 0 because it is optional.',
+    );
+
+    $form['multiple'] = $base + array(
+      '#title' => '#multiple, #default_value two',
+      '#default_value' => array('two'),
+      '#multiple' => TRUE,
+    );
+    $form['multiple_no_default'] = $base + array(
+      '#title' => '#multiple, no #default_value',
+      '#multiple' => TRUE,
+    );
+    $form['multiple_no_default_required'] = $base + array(
+      '#title' => '#multiple, #required, no #default_value',
+      '#required' => TRUE,
+      '#multiple' => TRUE,
+    );
+
+    $form['submit'] = array('#type' => 'submit', '#value' => 'Submit');
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $form_state['response'] = new JsonResponse($form_state['values']);
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestStatePersistForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestStatePersistForm.php
new file mode 100644
index 0000000..5d948b0
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestStatePersistForm.php
@@ -0,0 +1,51 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestStatePersistForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Form constructor for testing form state persistence.
+ */
+class FormTestStatePersistForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_state_persist';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['title'] = array(
+      '#type' => 'textfield',
+      '#title' => 'title',
+      '#default_value' => 'DEFAULT',
+      '#required' => TRUE,
+    );
+    $form_state['value'] = 'State persisted.';
+
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => t('Submit'),
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    drupal_set_message($form_state['value']);
+    $form_state['rebuild'] = TRUE;
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestStorageForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestStorageForm.php
new file mode 100644
index 0000000..dadee26
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestStorageForm.php
@@ -0,0 +1,126 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestStorageForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Component\Utility\String;
+use Drupal\Core\Form\FormBase;
+
+/**
+ * A multistep form for testing the form storage.
+ *
+ * It uses two steps for editing a virtual "thing". Any changes to it are saved
+ * in the form storage and have to be present during any step. By setting the
+ * request parameter "cache" the form can be tested with caching enabled, as
+ * it would be the case, if the form would contain some #ajax callbacks.
+ */
+class FormTestStorageForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_storage_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    if ($form_state['rebuild']) {
+      $form_state['input'] = array();
+    }
+    // Initialize
+    if (empty($form_state['storage'])) {
+      if (empty($form_state['input'])) {
+        $_SESSION['constructions'] = 0;
+      }
+      // Put the initial thing into the storage
+      $form_state['storage'] = array(
+        'thing' => array(
+          'title' => 'none',
+          'value' => '',
+        ),
+      );
+    }
+    // Count how often the form is constructed.
+    $_SESSION['constructions']++;
+    drupal_set_message("Form constructions: " . $_SESSION['constructions']);
+
+    $form['title'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Title',
+      '#default_value' => $form_state['storage']['thing']['title'],
+      '#required' => TRUE,
+    );
+    $form['value'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Value',
+      '#default_value' => $form_state['storage']['thing']['value'],
+      '#element_validate' => array(array($this, 'elementValidateValueCached')),
+    );
+    $form['continue_button'] = array(
+      '#type' => 'button',
+      '#value' => 'Reset',
+      // Rebuilds the form without keeping the values.
+    );
+    $form['continue_submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Continue submit',
+      '#submit' => array(array($this, 'continueSubmitForm')),
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Save',
+    );
+
+    if (\Drupal::request()->get('cache')) {
+      // Manually activate caching, so we can test that the storage keeps working
+      // when it's enabled.
+      $form_state['cache'] = TRUE;
+    }
+
+    return $form;
+  }
+
+  /**
+   * Form element validation handler for 'value' element.
+   *
+   * Tests updating of cached form storage during validation.
+   */
+  public function elementValidateValueCached($element, &$form_state) {
+    // If caching is enabled and we receive a certain value, change the storage.
+    // This presumes that another submitted form value triggers a validation error
+    // elsewhere in the form. Form API should still update the cached form storage
+    // though.
+    if (\Drupal::request()->get('cache') && $form_state['values']['value'] == 'change_title') {
+      $form_state['storage']['thing']['changed'] = TRUE;
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function continueSubmitForm(array &$form, array &$form_state) {
+    $form_state['storage']['thing']['title'] = $form_state['values']['title'];
+    $form_state['storage']['thing']['value'] = $form_state['values']['value'];
+    $form_state['rebuild'] = TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    drupal_set_message("Title: " . String::checkPlain($form_state['values']['title']));
+    drupal_set_message("Form constructions: " . $_SESSION['constructions']);
+    if (isset($form_state['storage']['thing']['changed'])) {
+      drupal_set_message("The thing has been changed.");
+    }
+    $form_state['redirect_route']['route_name'] = '<front>';
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestUrlForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestUrlForm.php
new file mode 100644
index 0000000..8e2c5a0
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestUrlForm.php
@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestUrlForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Symfony\Component\HttpFoundation\JsonResponse;
+
+/**
+ * Form constructor for testing #type 'url' elements.
+ */
+class FormTestUrlForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_url';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['url'] = array(
+      '#type' => 'url',
+      '#title' => 'Optional URL',
+      '#description' => 'An optional URL field.',
+    );
+    $form['url_required'] = array(
+      '#type' => 'url',
+      '#title' => 'Required URL',
+      '#description' => 'A required URL field.',
+      '#required' => TRUE,
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Submit',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $form_state['response'] = new JsonResponse($form_state['values']);
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestValidateForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestValidateForm.php
new file mode 100644
index 0000000..2e59a75
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestValidateForm.php
@@ -0,0 +1,81 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestValidateForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Drupal\form_test\Callbacks;
+
+/**
+ * Form builder for testing \Drupal\Core\Form\FormValidatorInterface::validateForm().
+ *
+ * Serves for testing form processing and alterations by form validation
+ * handlers, especially for the case of a validation error:
+ * - form_set_value() should be able to alter submitted values in
+ *   $form_state['values'] without affecting the form element.
+ * - #element_validate handlers should be able to alter the $element in the form
+ *   structure and the alterations should be contained in the rebuilt form.
+ * - #validate handlers should be able to alter the $form and the alterations
+ *   should be contained in the rebuilt form.
+ */
+class FormTestValidateForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_validate_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $object = new Callbacks();
+
+    $form['name'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Name',
+      '#default_value' => '',
+      '#element_validate' => array(array($object, 'validateName')),
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Save',
+    );
+
+    // To simplify this test, enable form caching and use form storage to
+    // remember our alteration.
+    $form_state['cache'] = TRUE;
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, array &$form_state) {
+    if ($form_state['values']['name'] == 'validate') {
+      // Alter the form element.
+      $form['name']['#value'] = '#value changed by #validate';
+      // Alter the submitted value in $form_state.
+      form_set_value($form['name'], 'value changed by form_set_value() in #validate', $form_state);
+      // Output the element's value from $form_state.
+      drupal_set_message(t('@label value: @value', array('@label' => $form['name']['#title'], '@value' => $form_state['values']['name'])));
+
+      // Trigger a form validation error to see our changes.
+      form_set_error('', $form_state);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestValidateRequiredForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestValidateRequiredForm.php
new file mode 100644
index 0000000..65cb030
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestValidateRequiredForm.php
@@ -0,0 +1,92 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestValidateRequiredForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Form constructor to test the #required property.
+ */
+class FormTestValidateRequiredForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_validate_required_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $options = array('foo' => 'foo', 'bar' => 'bar');
+    $validate = array(array($this, 'elementValidateRequired'));
+
+    $form['textfield'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Name',
+      '#required' => TRUE,
+      '#required_error' => t('Please enter a name.'),
+    );
+    $form['checkboxes'] = array(
+      '#type' => 'checkboxes',
+      '#title' => 'Checkboxes',
+      '#options' => $options,
+      '#required' => TRUE,
+      '#form_test_required_error' => t('Please choose at least one option.'),
+      '#element_validate' => $validate,
+    );
+    $form['select'] = array(
+      '#type' => 'select',
+      '#title' => 'Select',
+      '#options' => $options,
+      '#required' => TRUE,
+      '#form_test_required_error' => t('Please select something.'),
+      '#element_validate' => $validate,
+    );
+    $form['radios'] = array(
+      '#type' => 'radios',
+      '#title' => 'Radios',
+      '#options' => $options,
+      '#required' => TRUE,
+    );
+    $form['radios_optional'] = array(
+      '#type' => 'radios',
+      '#title' => 'Radios (optional)',
+      '#options' => $options,
+    );
+    $form['radios_optional_default_value_false'] = array(
+      '#type' => 'radios',
+      '#title' => 'Radios (optional, with a default value of FALSE)',
+      '#options' => $options,
+      '#default_value' => FALSE,
+    );
+    $form['actions'] = array('#type' => 'actions');
+    $form['actions']['submit'] = array('#type' => 'submit', '#value' => 'Submit');
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function elementValidateRequired($element, &$form_state) {
+    // Set a custom validation error on the #required element.
+    if (!empty($element['#required_but_empty']) && isset($element['#form_test_required_error'])) {
+      form_error($element, $form_state, $element['#form_test_required_error']);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    drupal_set_message('The form_test_validate_required_form form was submitted successfully.');
+  }
+
+}
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestValidateRequiredNoTitleForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestValidateRequiredNoTitleForm.php
new file mode 100644
index 0000000..25e5076
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestValidateRequiredNoTitleForm.php
@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestValidateRequiredNoTitleForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Form constructor to test the #required property without #title.
+ */
+class FormTestValidateRequiredNoTitleForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_validate_required_form_no_title';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['textfield'] = array(
+      '#type' => 'textfield',
+      '#required' => TRUE,
+    );
+    $form['actions'] = array('#type' => 'actions');
+    $form['actions']['submit'] = array('#type' => 'submit', '#value' => 'Submit');
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    drupal_set_message('The form_test_validate_required_form_no_title form was submitted successfully.');
+  }
+
+}