diff --git a/core/modules/system/tests/modules/test_page_test/src/Form/TestForm.php b/core/modules/system/tests/modules/test_page_test/src/Form/TestForm.php
index 24a9bdb58b..98ddc7cb8b 100644
--- a/core/modules/system/tests/modules/test_page_test/src/Form/TestForm.php
+++ b/core/modules/system/tests/modules/test_page_test/src/Form/TestForm.php
@@ -64,6 +64,18 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#default_value' => 2,
     ];
 
+    $form['duplicate_button'] = [
+      '#type' => 'submit',
+      '#name' => 'duplicate_button',
+      '#value' => 'Duplicate button 1',
+    ];
+
+    $form['duplicate_button_2'] = [
+      '#type' => 'submit',
+      '#name' => 'duplicate_button',
+      '#value' => 'Duplicate button 2',
+    ];
+
     $form['save'] = [
       '#type' => 'submit',
       '#value' => $this->t('Save'),
diff --git a/core/modules/user/src/Tests/UserAdminLanguageTest.php b/core/modules/user/tests/src/Functional/UserAdminLanguageTest.php
similarity index 86%
rename from core/modules/user/src/Tests/UserAdminLanguageTest.php
rename to core/modules/user/tests/src/Functional/UserAdminLanguageTest.php
index cd6cc657bf..414f159770 100644
--- a/core/modules/user/src/Tests/UserAdminLanguageTest.php
+++ b/core/modules/user/tests/src/Functional/UserAdminLanguageTest.php
@@ -1,16 +1,16 @@
 <?php
 
-namespace Drupal\user\Tests;
+namespace Drupal\Tests\user\Functional;
 
 use Drupal\Core\Language\LanguageInterface;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Tests users' ability to change their own administration language.
  *
  * @group user
  */
-class UserAdminLanguageTest extends WebTestBase {
+class UserAdminLanguageTest extends BrowserTestBase {
 
   /**
    * A user with permission to access admin pages and administer languages.
@@ -50,7 +50,7 @@ public function testUserAdminLanguageConfigurationNotAvailableWithOnlyOneLanguag
     $path = 'user/' . $this->adminUser->id() . '/edit';
     $this->drupalGet($path);
     // Ensure administration pages language settings widget is not available.
-    $this->assertNoFieldByXPath($this->constructFieldXpath('id', 'edit-preferred-admin-langcode'), NULL, 'Administration pages language selector not available.');
+    $this->assertNull($this->getSession()->getPage()->findField('edit-preferred-admin-langcode'));
   }
 
   /**
@@ -64,13 +64,13 @@ public function testUserAdminLanguageConfigurationAvailableWithAdminLanguageNego
     // Checks with user administration pages language negotiation disabled.
     $this->drupalGet($path);
     // Ensure administration pages language settings widget is not available.
-    $this->assertNoFieldByXPath($this->constructFieldXpath('id', 'edit-preferred-admin-langcode'), NULL, 'Administration pages language selector not available.');
+    $this->assertNull($this->getSession()->getPage()->findField('edit-preferred-admin-langcode'));
 
     // Checks with user administration pages language negotiation enabled.
     $this->setLanguageNegotiation();
     $this->drupalGet($path);
     // Ensure administration pages language settings widget is available.
-    $this->assertFieldByXPath($this->constructFieldXpath('id', 'edit-preferred-admin-langcode'), NULL, 'Administration pages language selector is available.');
+    $this->assertNotNull($this->getSession()->getPage()->findField('edit-preferred-admin-langcode'));
   }
 
   /**
@@ -91,13 +91,13 @@ public function testUserAdminLanguageConfigurationAvailableIfAdminLanguageNegoti
     $path = 'user/' . $this->adminUser->id() . '/edit';
     $this->drupalGet($path);
     // Ensure administration pages language setting is visible for admin.
-    $this->assertFieldByXPath($this->constructFieldXpath('id', 'edit-preferred-admin-langcode'), NULL, 'Administration pages language selector available for admins.');
+    $this->assertNotNull($this->getSession()->getPage()->findField( 'edit-preferred-admin-langcode'));
 
     // Ensure administration pages language setting is hidden for non-admins.
     $this->drupalLogin($this->regularUser);
     $path = 'user/' . $this->regularUser->id() . '/edit';
     $this->drupalGet($path);
-    $this->assertNoFieldByXPath($this->constructFieldXpath('id', 'edit-preferred-admin-langcode'), NULL, 'Administration pages language selector not available for regular user.');
+    $this->assertNull($this->getSession()->getPage()->findField('edit-preferred-admin-langcode'));
   }
 
   /**
diff --git a/core/modules/user/src/Tests/UserBlocksTest.php b/core/modules/user/tests/src/Functional/UserBlocksTest.php
similarity index 71%
rename from core/modules/user/src/Tests/UserBlocksTest.php
rename to core/modules/user/tests/src/Functional/UserBlocksTest.php
index 0a4c619da6..6c2ae97609 100644
--- a/core/modules/user/src/Tests/UserBlocksTest.php
+++ b/core/modules/user/tests/src/Functional/UserBlocksTest.php
@@ -1,16 +1,16 @@
 <?php
 
-namespace Drupal\user\Tests;
+namespace Drupal\Tests\user\Functional;
 
 use Drupal\dynamic_page_cache\EventSubscriber\DynamicPageCacheSubscriber;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Tests user blocks.
  *
  * @group user
  */
-class UserBlocksTest extends WebTestBase {
+class UserBlocksTest extends BrowserTestBase {
 
   /**
    * Modules to enable.
@@ -69,7 +69,7 @@ public function testUserLoginBlock() {
     // Log in using the block.
     $edit = [];
     $edit['name'] = $user->getUsername();
-    $edit['pass'] = $user->pass_raw;
+    $edit['pass'] = $user->passRaw;
     $this->drupalPostForm('admin/people/permissions', $edit, t('Log in'));
     $this->assertNoText(t('User login'), 'Logged in.');
 
@@ -121,46 +121,4 @@ public function testUserLoginBlock() {
     $this->assertNoText(t('Unrecognized username or password. Forgot your password?'));
   }
 
-  /**
-   * Test the Who's Online block.
-   */
-  public function testWhosOnlineBlock() {
-    $block = $this->drupalPlaceBlock('views_block:who_s_online-who_s_online_block');
-
-    // Generate users.
-    $user1 = $this->drupalCreateUser(['access user profiles']);
-    $user2 = $this->drupalCreateUser([]);
-    $user3 = $this->drupalCreateUser([]);
-
-    // Update access of two users to be within the active timespan.
-    $this->updateAccess($user1->id());
-    $this->updateAccess($user2->id(), REQUEST_TIME + 1);
-
-    // Insert an inactive user who should not be seen in the block, and ensure
-    // that the admin user used in setUp() does not appear.
-    $inactive_time = REQUEST_TIME - (15 * 60) - 1;
-    $this->updateAccess($user3->id(), $inactive_time);
-    $this->updateAccess($this->adminUser->id(), $inactive_time);
-
-    // Test block output.
-    \Drupal::currentUser()->setAccount($user1);
-    $content = entity_view($block, 'block');
-    $this->setRawContent(\Drupal::service('renderer')->renderRoot($content));
-    $this->assertRaw(t('2 users'), 'Correct number of online users (2 users).');
-    $this->assertText($user1->getUsername(), 'Active user 1 found in online list.');
-    $this->assertText($user2->getUsername(), 'Active user 2 found in online list.');
-    $this->assertNoText($user3->getUsername(), 'Inactive user not found in online list.');
-    $this->assertTrue(strpos($this->getRawContent(), $user1->getUsername()) > strpos($this->getRawContent(), $user2->getUsername()), 'Online users are ordered correctly.');
-  }
-
-  /**
-   * Updates the access column for a user.
-   */
-  private function updateAccess($uid, $access = REQUEST_TIME) {
-    db_update('users_field_data')
-      ->condition('uid', $uid)
-      ->fields(['access' => $access])
-      ->execute();
-  }
-
 }
diff --git a/core/modules/user/src/Tests/UserCreateTest.php b/core/modules/user/tests/src/Functional/UserCreateTest.php
similarity index 94%
rename from core/modules/user/src/Tests/UserCreateTest.php
rename to core/modules/user/tests/src/Functional/UserCreateTest.php
index 7b534435a0..fb7e996e3f 100644
--- a/core/modules/user/src/Tests/UserCreateTest.php
+++ b/core/modules/user/tests/src/Functional/UserCreateTest.php
@@ -1,18 +1,22 @@
 <?php
 
-namespace Drupal\user\Tests;
+namespace Drupal\Tests\user\Functional;
 
 use Drupal\field\Entity\FieldConfig;
-use Drupal\simpletest\WebTestBase;
 use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\Tests\BrowserTestBase;
+use Drupal\Core\Test\AssertMailTrait;
 
 /**
  * Tests the create user administration page.
  *
  * @group user
  */
-class UserCreateTest extends WebTestBase {
+class UserCreateTest extends BrowserTestBase {
 
+  use AssertMailTrait {
+    getMails as drupalGetMails;
+  }
   /**
    * Modules to enable.
    *
@@ -109,7 +113,7 @@ public function testUserAdd() {
       $this->drupalGet('admin/people');
       $this->assertText($edit['name'], 'User found in list of users');
       $user = user_load_by_name($name);
-      $this->assertEqual($user->isActive(), 'User is not blocked');
+      $this->assertTrue($user->isActive(), 'User is not blocked');
     }
 
     // Test that the password '0' is considered a password.
diff --git a/core/modules/user/src/Tests/UserPasswordResetTest.php b/core/modules/user/tests/src/Functional/UserPasswordResetTest.php
similarity index 97%
rename from core/modules/user/src/Tests/UserPasswordResetTest.php
rename to core/modules/user/tests/src/Functional/UserPasswordResetTest.php
index 528d38bc96..fb25317075 100644
--- a/core/modules/user/src/Tests/UserPasswordResetTest.php
+++ b/core/modules/user/tests/src/Functional/UserPasswordResetTest.php
@@ -1,11 +1,13 @@
 <?php
 
-namespace Drupal\user\Tests;
+namespace Drupal\Tests\user\Functional;
 
 use Drupal\Component\Render\FormattableMarkup;
 use Drupal\Core\Url;
-use Drupal\system\Tests\Cache\PageCacheTagsTestBase;
+use \Drupal\Tests\system\Functional\Cache\PageCacheTagsTestBase;
 use Drupal\user\Entity\User;
+use Drupal\Core\Test\AssertMailTrait;
+use Drupal\Tests\TestFileCreationTrait;
 
 /**
  * Ensure that password reset methods work as expected.
@@ -14,6 +16,13 @@
  */
 class UserPasswordResetTest extends PageCacheTagsTestBase {
 
+  use AssertMailTrait {
+    getMails as drupalGetMails;
+  }
+  use TestFileCreationTrait {
+    getTestFiles as drupalGetTestFiles;
+  }
+
   /**
    * The profile to install as a basis for testing.
    *
@@ -54,7 +63,7 @@ protected function setUp() {
     $this->drupalLogin($account);
 
     $this->account = User::load($account->id());
-    $this->account->pass_raw = $account->pass_raw;
+    $this->account->passRaw = $account->passRaw;
     $this->drupalLogout();
 
     // Set the last login time that is used to generate the one-time link so
@@ -120,7 +129,7 @@ public function testUserPasswordReset() {
     $edit = [
       'files[user_picture_0]' => drupal_realpath($image->uri),
     ];
-    $this->drupalPostAjaxForm(NULL, $edit, 'user_picture_0_upload_button');
+    $this->drupalPostForm(NULL, $edit, 'Upload');
 
     // Change the forgotten password.
     $password = user_password();
diff --git a/core/modules/user/src/Tests/UserRegistrationTest.php b/core/modules/user/tests/src/Functional/UserRegistrationTest.php
similarity index 72%
rename from core/modules/user/src/Tests/UserRegistrationTest.php
rename to core/modules/user/tests/src/Functional/UserRegistrationTest.php
index ca7a4f0c89..5f8b00bf65 100644
--- a/core/modules/user/src/Tests/UserRegistrationTest.php
+++ b/core/modules/user/tests/src/Functional/UserRegistrationTest.php
@@ -1,20 +1,19 @@
 <?php
 
-namespace Drupal\user\Tests;
+namespace Drupal\Tests\user\Functional;
 
 use Drupal\Core\Entity\Entity\EntityFormDisplay;
 use Drupal\Component\Utility\SafeMarkup;
-use Drupal\Core\Field\FieldStorageDefinitionInterface;
 use Drupal\field\Entity\FieldConfig;
 use Drupal\field\Entity\FieldStorageConfig;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Tests registration of user under different configurations.
  *
  * @group user
  */
-class UserRegistrationTest extends WebTestBase {
+class UserRegistrationTest extends BrowserTestBase {
 
   /**
    * Modules to enable.
@@ -254,7 +253,7 @@ public function testRegistrationDefaultValues() {
     $new_user = reset($accounts);
     $this->assertEqual($new_user->getUsername(), $name, 'Username matches.');
     $this->assertEqual($new_user->getEmail(), $mail, 'Email address matches.');
-    $this->assertTrue(($new_user->getCreatedTime() > REQUEST_TIME - 20 ), 'Correct creation time.');
+    $this->assertTrue(($new_user->getCreatedTime() > REQUEST_TIME - 20), 'Correct creation time.');
     $this->assertEqual($new_user->isActive(), $config_user_settings->get('register') == USER_REGISTER_VISITORS ? 1 : 0, 'Correct status field.');
     $this->assertEqual($new_user->getTimezone(), $config_system_date->get('timezone.default'), 'Correct time zone field.');
     $this->assertEqual($new_user->langcode->value, \Drupal::languageManager()->getDefaultLanguage()->getId(), 'Correct language field.');
@@ -281,105 +280,6 @@ public function testUniqueFields() {
   }
 
   /**
-   * Tests Field API fields on user registration forms.
-   */
-  public function testRegistrationWithUserFields() {
-    // Create a field on 'user' entity type.
-    $field_storage = FieldStorageConfig::create([
-      'field_name' => 'test_user_field',
-      'entity_type' => 'user',
-      'type' => 'test_field',
-      'cardinality' => 1,
-    ]);
-    $field_storage->save();
-    $field = FieldConfig::create([
-      'field_storage' => $field_storage,
-      'label' => 'Some user field',
-      'bundle' => 'user',
-      'required' => TRUE,
-    ]);
-    $field->save();
-    entity_get_form_display('user', 'user', 'default')
-      ->setComponent('test_user_field', ['type' => 'test_field_widget'])
-      ->save();
-    entity_get_form_display('user', 'user', 'register')
-      ->save();
-
-    // Check that the field does not appear on the registration form.
-    $this->drupalGet('user/register');
-    $this->assertNoText($field->label(), 'The field does not appear on user registration form');
-    $this->assertCacheTag('config:core.entity_form_display.user.user.register');
-    $this->assertCacheTag('config:user.settings');
-
-    // Have the field appear on the registration form.
-    entity_get_form_display('user', 'user', 'register')
-      ->setComponent('test_user_field', ['type' => 'test_field_widget'])
-      ->save();
-
-    $this->drupalGet('user/register');
-    $this->assertText($field->label(), 'The field appears on user registration form');
-    $this->assertRegistrationFormCacheTagsWithUserFields();
-
-    // Check that validation errors are correctly reported.
-    $edit = [];
-    $edit['name'] = $name = $this->randomMachineName();
-    $edit['mail'] = $mail = $edit['name'] . '@example.com';
-    // Missing input in required field.
-    $edit['test_user_field[0][value]'] = '';
-    $this->drupalPostForm(NULL, $edit, t('Create new account'));
-    $this->assertRegistrationFormCacheTagsWithUserFields();
-    $this->assertRaw(t('@name field is required.', ['@name' => $field->label()]), 'Field validation error was correctly reported.');
-    // Invalid input.
-    $edit['test_user_field[0][value]'] = '-1';
-    $this->drupalPostForm(NULL, $edit, t('Create new account'));
-    $this->assertRegistrationFormCacheTagsWithUserFields();
-    $this->assertRaw(t('%name does not accept the value -1.', ['%name' => $field->label()]), 'Field validation error was correctly reported.');
-
-    // Submit with valid data.
-    $value = rand(1, 255);
-    $edit['test_user_field[0][value]'] = $value;
-    $this->drupalPostForm(NULL, $edit, t('Create new account'));
-    // Check user fields.
-    $accounts = $this->container->get('entity_type.manager')->getStorage('user')
-      ->loadByProperties(['name' => $name, 'mail' => $mail]);
-    $new_user = reset($accounts);
-    $this->assertEqual($new_user->test_user_field->value, $value, 'The field value was correctly saved.');
-
-    // Check that the 'add more' button works.
-    $field_storage->setCardinality(FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
-    $field_storage->save();
-    foreach (['js', 'nojs'] as $js) {
-      $this->drupalGet('user/register');
-      $this->assertRegistrationFormCacheTagsWithUserFields();
-      // Add two inputs.
-      $value = rand(1, 255);
-      $edit = [];
-      $edit['test_user_field[0][value]'] = $value;
-      if ($js == 'js') {
-        $this->drupalPostAjaxForm(NULL, $edit, 'test_user_field_add_more');
-        $this->drupalPostAjaxForm(NULL, $edit, 'test_user_field_add_more');
-      }
-      else {
-        $this->drupalPostForm(NULL, $edit, t('Add another item'));
-        $this->drupalPostForm(NULL, $edit, t('Add another item'));
-      }
-      // Submit with three values.
-      $edit['test_user_field[1][value]'] = $value + 1;
-      $edit['test_user_field[2][value]'] = $value + 2;
-      $edit['name'] = $name = $this->randomMachineName();
-      $edit['mail'] = $mail = $edit['name'] . '@example.com';
-      $this->drupalPostForm(NULL, $edit, t('Create new account'));
-      // Check user fields.
-      $accounts = $this->container->get('entity_type.manager')->getStorage('user')
-        ->loadByProperties(['name' => $name, 'mail' => $mail]);
-      $new_user = reset($accounts);
-      $this->assertEqual($new_user->test_user_field[0]->value, $value, format_string('@js : The field value was correctly saved.', ['@js' => $js]));
-      $this->assertEqual($new_user->test_user_field[1]->value, $value + 1, format_string('@js : The field value was correctly saved.', ['@js' => $js]));
-      $this->assertEqual($new_user->test_user_field[2]->value, $value + 2, format_string('@js : The field value was correctly saved.', ['@js' => $js]));
-    }
-  }
-
-  /**
    * Asserts the presence of cache tags on registration form with user fields.
    */
   protected function assertRegistrationFormCacheTagsWithUserFields() {
diff --git a/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
index 08a2d8ea19..f768b71ad5 100644
--- a/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
+++ b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
@@ -2,7 +2,6 @@
 
 namespace Drupal\FunctionalTests;
 
-use Behat\Mink\Exception\ElementNotFoundException;
 use Behat\Mink\Exception\ExpectationException;
 use Behat\Mink\Selector\Xpath\Escaper;
 use Drupal\Component\Render\FormattableMarkup;
@@ -220,13 +219,11 @@ protected function assertResponse($code) {
    *
    * @deprecated Scheduled for removal in Drupal 9.0.0.
    *   Use $this->assertSession()->fieldExists() or
+   *   $this->assertSession()->buttonExists() or
    *   $this->assertSession()->fieldValueEquals() instead.
    */
   protected function assertFieldByName($name, $value = NULL) {
-    $this->assertSession()->fieldExists($name);
-    if ($value !== NULL) {
-      $this->assertSession()->fieldValueEquals($name, (string) $value);
-    }
+    $this->assertFieldByXPath($this->constructFieldXpath('name', $name), $value);
   }
 
   /**
@@ -242,15 +239,11 @@ protected function assertFieldByName($name, $value = NULL) {
    *
    * @deprecated Scheduled for removal in Drupal 9.0.0.
    *   Use $this->assertSession()->fieldNotExists() or
+   *   $this->assertSession()->buttonNotExists() or
    *   $this->assertSession()->fieldValueNotEquals() instead.
    */
   protected function assertNoFieldByName($name, $value = '') {
-    if ($this->getSession()->getPage()->findField($name) && isset($value)) {
-      $this->assertSession()->fieldValueNotEquals($name, (string) $value);
-    }
-    else {
-      $this->assertSession()->fieldNotExists($name);
-    }
+    $this->assertNoFieldByXPath($this->constructFieldXpath('name', $name), $value);
   }
 
   /**
@@ -268,19 +261,11 @@ protected function assertNoFieldByName($name, $value = '') {
    *
    * @deprecated Scheduled for removal in Drupal 9.0.0.
    *   Use $this->assertSession()->fieldExists() or
+   *   $this->assertSession()->buttonExists() or
    *   $this->assertSession()->fieldValueEquals() instead.
    */
   protected function assertFieldById($id, $value = '') {
-    $xpath = $this->assertSession()->buildXPathQuery('//textarea[@id=:value]|//input[@id=:value]|//select[@id=:value]', [':value' => $id]);
-    $field = $this->getSession()->getPage()->find('xpath', $xpath);
-
-    if (empty($field)) {
-      throw new ElementNotFoundException($this->getSession()->getDriver(), 'form field', 'id', $field);
-    }
-
-    if ($value !== NULL) {
-      $this->assertEquals($value, $field->getValue());
-    }
+    $this->assertFieldByXPath($this->constructFieldXpath('id', $id), $value);
   }
 
   /**
@@ -290,23 +275,25 @@ protected function assertFieldById($id, $value = '') {
    *   Name or ID of field to assert.
    *
    * @deprecated Scheduled for removal in Drupal 9.0.0.
-   *   Use $this->assertSession()->fieldExists() instead.
+   *   Use $this->assertSession()->fieldExists() or
+   *   $this->assertSession()->buttonExists() instead.
    */
   protected function assertField($field) {
-    $this->assertSession()->fieldExists($field);
+    $this->assertFieldByXPath($this->constructFieldXpath('name', $field) . '|' . $this->constructFieldXpath('id', $field));
   }
 
   /**
-   * Asserts that a field exists with the given name or ID does NOT exist.
+   * Asserts that a field does NOT exist with the given name or ID.
    *
    * @param string $field
    *   Name or ID of field to assert.
    *
    * @deprecated Scheduled for removal in Drupal 9.0.0.
-   *   Use $this->assertSession()->fieldNotExists() instead.
+   *   Use $this->assertSession()->fieldNotExists() or
+   *   $this->assertSession()->buttonNotExists() instead.
    */
   protected function assertNoField($field) {
-    $this->assertSession()->fieldNotExists($field);
+    $this->assertNoFieldByXPath($this->constructFieldXpath('name', $field) . '|' . $this->constructFieldXpath('id', $field));
   }
 
   /**
@@ -427,23 +414,11 @@ protected function assertNoLinkByHref($href) {
    *
    * @deprecated Scheduled for removal in Drupal 9.0.0.
    *   Use $this->assertSession()->fieldNotExists() or
+   *   $this->assertSession()->buttonNotExists() or
    *   $this->assertSession()->fieldValueNotEquals() instead.
    */
   protected function assertNoFieldById($id, $value = '') {
-    $xpath = $this->assertSession()->buildXPathQuery('//textarea[@id=:value]|//input[@id=:value]|//select[@id=:value]', [':value' => $id]);
-    $field = $this->getSession()->getPage()->find('xpath', $xpath);
-
-    // Return early if the field could not be found as expected.
-    if ($field === NULL) {
-      return;
-    }
-
-    if (!isset($value)) {
-      throw new ExpectationException(sprintf('Id "%s" appears on this page, but it should not.', $id), $this->getSession()->getDriver());
-    }
-    elseif ($value === $field->getValue()) {
-      throw new ExpectationException(sprintf('Failed asserting that %s is not equal to %s', $field->getValue(), $value), $this->getSession()->getDriver());
-    }
+    $this->assertNoFieldByXPath($this->constructFieldXpath('id', $id), $value);
   }
 
   /**
@@ -585,25 +560,32 @@ protected function assertFieldByXPath($xpath, $value = NULL, $message = '') {
    *   (optional) A message to display with the assertion. Do not translate
    *   messages with t().
    *
+   * @throws \Behat\Mink\Exception\ExpectationException
+   *
    * @deprecated Scheduled for removal in Drupal 9.0.0.
    *   Use $this->xpath() instead and assert that the result is empty.
    */
   protected function assertNoFieldByXPath($xpath, $value = NULL, $message = '') {
     $fields = $this->xpath($xpath);
 
-    // If value specified then check array for match.
-    $found = TRUE;
-    if (isset($value)) {
-      $found = FALSE;
-      if ($fields) {
-        foreach ($fields as $field) {
-          if ($field->getAttribute('value') == $value) {
-            $found = TRUE;
-          }
+    if (!empty($fields)) {
+      if (isset($value)) {
+        $found = FALSE;
+        try {
+          $this->assertFieldsByValue($fields, $value);
+          $found = TRUE;
+        }
+        catch (\Exception $e) {
+        }
+
+        if ($found) {
+          throw new ExpectationException(sprintf('The field resulting from %s was found with the provided value %s.', $xpath, $value), $this->getSession()->getDriver());
         }
       }
+      else {
+        throw new ExpectationException(sprintf('The field resulting from %s was found.', $xpath), $this->getSession()->getDriver());
+      }
     }
-    return $this->assertFalse($fields && $found, $message);
   }
 
   /**
@@ -629,7 +611,15 @@ protected function assertFieldsByValue($fields, $value = NULL, $message = '') {
       $found = FALSE;
       if ($fields) {
         foreach ($fields as $field) {
-          if ($field->getAttribute('value') == $value) {
+          if ($field->getAttribute('type') == 'checkbox') {
+            if (is_bool($value)) {
+              $found = $field->isChecked() == $value;
+            }
+            else {
+              $found = TRUE;
+            }
+          }
+          elseif ($field->getAttribute('value') == $value) {
             // Input element with correct value.
             $found = TRUE;
           }
@@ -637,7 +627,7 @@ protected function assertFieldsByValue($fields, $value = NULL, $message = '') {
             // Select element with an option.
             $found = TRUE;
           }
-          elseif ($field->getText() == $value) {
+          elseif ($field->getTagName() !== 'input' && $field->getText() == $value) {
             // Text area with correct text.
             $found = TRUE;
           }
@@ -789,6 +779,25 @@ protected function buildXPathQuery($xpath, array $args = []) {
   }
 
   /**
+   * Helper: Constructs an XPath for the given set of attributes and value.
+   *
+   * @param string $attribute
+   *   Field attributes.
+   * @param string $value
+   *   Value of field.
+   *
+   * @return string
+   *   XPath for specified values.
+   *
+   * @deprecated Scheduled for removal in Drupal 9.0.0.
+   *   Use $this->getSession()->getPage()->findField() instead.
+   */
+  protected function constructFieldXpath($attribute, $value) {
+    $xpath = '//textarea[@' . $attribute . '=:value]|//input[@' . $attribute . '=:value]|//select[@' . $attribute . '=:value]';
+    return $this->buildXPathQuery($xpath, [':value' => $value]);
+  }
+
+  /**
    * Gets the current raw content.
    *
    * @deprecated Scheduled for removal in Drupal 9.0.0.
diff --git a/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php b/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
index 2701dcb0bf..2195dc9097 100644
--- a/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
+++ b/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
@@ -223,7 +223,7 @@ public function testLegacyXpathAsserts() {
       $this->assertNoFieldByXPath("//input[@id = 'edit-name']");
       $this->fail('The "edit-name" field was not found.');
     }
-    catch (\PHPUnit_Framework_ExpectationFailedException $e) {
+    catch (ExpectationException $e) {
       $this->pass('assertNoFieldByXPath correctly failed. The "edit-name" field was found.');
     }
 
@@ -239,7 +239,7 @@ public function testLegacyXpathAsserts() {
   /**
    * Tests legacy field asserts using textfields.
    */
-  public function testLegacyFieldAssertsWithTextfields() {
+  public function testLegacyFieldAssertsForTextfields() {
     $this->drupalGet('test-field-xpath');
 
     // *** 1. assertNoField().
@@ -272,7 +272,7 @@ public function testLegacyFieldAssertsWithTextfields() {
       $this->assertField('invalid_name_and_id');
       $this->fail('The "invalid_name_and_id" field was found.');
     }
-    catch (ExpectationException $e) {
+    catch (\PHPUnit_Framework_ExpectationFailedException $e) {
       $this->pass('assertField correctly failed. The "invalid_name_and_id" field was not found.');
     }
 
@@ -361,7 +361,7 @@ public function testLegacyFieldAssertsWithTextfields() {
       $this->assertFieldByName('non-existing-name');
       $this->fail('The "non-existing-name" field was found.');
     }
-    catch (ExpectationException $e) {
+    catch (\PHPUnit_Framework_ExpectationFailedException $e) {
       $this->pass('The "non-existing-name" field was not found');
     }
 
@@ -370,15 +370,15 @@ public function testLegacyFieldAssertsWithTextfields() {
       $this->assertFieldByName('name', 'not the value');
       $this->fail('The "name" field with incorrect value was found.');
     }
-    catch (ExpectationException $e) {
+    catch (\PHPUnit_Framework_ExpectationFailedException $e) {
       $this->pass('assertFieldByName correctly failed. The "name" field with incorrect value was not found.');
     }
   }
 
   /**
-   * Tests legacy field asserts on other types of field.
+   * Tests legacy field asserts for options field type.
    */
-  public function testLegacyFieldAssertsWithNonTextfields() {
+  public function testLegacyFieldAssertsForOptions() {
     $this->drupalGet('test-field-xpath');
 
     // Option field type.
@@ -425,8 +425,14 @@ public function testLegacyFieldAssertsWithNonTextfields() {
     catch (\PHPUnit_Framework_ExpectationFailedException $e) {
       $this->pass($e->getMessage());
     }
+  }
+
+  /**
+   * Tests legacy field asserts for button field type.
+   */
+  public function testLegacyFieldAssertsForButton() {
+    $this->drupalGet('test-field-xpath');
 
-    // Button field type.
     $this->assertFieldById('edit-save', NULL);
     // Test that the assertion fails correctly if the field value is passed in
     // rather than the id.
@@ -434,7 +440,7 @@ public function testLegacyFieldAssertsWithNonTextfields() {
       $this->assertFieldById('Save', NULL);
       $this->fail('The field with id of "Save" was found.');
     }
-    catch (ExpectationException $e) {
+    catch (\PHPUnit_Framework_ExpectationFailedException $e) {
       $this->pass($e->getMessage());
     }
 
@@ -449,7 +455,27 @@ public function testLegacyFieldAssertsWithNonTextfields() {
       $this->pass($e->getMessage());
     }
 
-    // Checkbox field type.
+    // Test that multiple fields with the same name are validated correctly.
+    $this->assertFieldByName('duplicate_button', 'Duplicate button 1');
+    $this->assertFieldByName('duplicate_button', 'Duplicate button 2');
+    $this->assertNoFieldByName('duplicate_button', 'Rabbit');
+
+    try {
+      $this->assertNoFieldByName('duplicate_button', 'Duplicate button 2');
+      $this->fail('The "duplicate_button" field with the value Duplicate button 2 was not found.');
+    }
+    catch (ExpectationException $e) {
+      $this->pass('assertNoFieldByName correctly failed. The "duplicate_button" field with the value Duplicate button 2 was found.');
+    }
+  }
+
+  /**
+   * Tests legacy field asserts for checkbox field type.
+   */
+  public function testLegacyFieldAssertsForCheckbox() {
+    $this->drupalGet('test-field-xpath');
+
+    // Part 1 - Test by name.
     // Test that checkboxes are found/not found correctly by name, when using
     // TRUE or FALSE to match their 'checked' state.
     $this->assertFieldByName('checkbox_enabled', TRUE);
@@ -462,6 +488,24 @@ public function testLegacyFieldAssertsWithNonTextfields() {
     $this->assertFieldByName('checkbox_enabled', NULL);
     $this->assertFieldByName('checkbox_disabled', NULL);
 
+    // Test that checkboxes are found by name when passing no second parameter.
+    $this->assertFieldByName('checkbox_enabled');
+    $this->assertFieldByName('checkbox_disabled');
+
+    // Test that we have legacy support.
+    $this->assertFieldByName('checkbox_enabled', '1');
+    $this->assertFieldByName('checkbox_disabled', '');
+
+    // Test that the assertion fails correctly when using NULL to ignore state.
+    try {
+      $this->assertNoFieldByName('checkbox_enabled', NULL);
+      $this->fail('The "checkbox_enabled" field was not found by name, using NULL value.');
+    }
+    catch (ExpectationException $e) {
+      $this->pass('assertNoFieldByName failed correctly. The "checkbox_enabled" field was found using NULL value.');
+    }
+
+    // Part 2 - Test by ID.
     // Test that checkboxes are found/not found correctly by ID, when using
     // TRUE or FALSE to match their 'checked' state.
     $this->assertFieldById('edit-checkbox-enabled', TRUE);
@@ -469,19 +513,18 @@ public function testLegacyFieldAssertsWithNonTextfields() {
     $this->assertNoFieldById('edit-checkbox-enabled', FALSE);
     $this->assertNoFieldById('edit-checkbox-disabled', TRUE);
 
-    // Test that checkboxes are found by by ID, when using NULL to ignore the
+    // Test that checkboxes are found by ID, when using NULL to ignore the
     // 'checked' state.
     $this->assertFieldById('edit-checkbox-enabled', NULL);
     $this->assertFieldById('edit-checkbox-disabled', NULL);
 
-    // Test that the assertion fails correctly when using NULL to ignore state.
-    try {
-      $this->assertNoFieldByName('checkbox_enabled', NULL);
-      $this->fail('The "checkbox_enabled" field was not found by name, using NULL value.');
-    }
-    catch (ExpectationException $e) {
-      $this->pass('assertNoFieldByName failed correctly. The "checkbox_enabled" field was found using NULL value.');
-    }
+    // Test that checkboxes are found by ID when passing no second parameter.
+    $this->assertFieldById('edit-checkbox-enabled');
+    $this->assertFieldById('edit-checkbox-disabled');
+
+    // Test that we have legacy support.
+    $this->assertFieldById('edit-checkbox-enabled', '1');
+    $this->assertFieldById('edit-checkbox-disabled', '');
 
     // Test that the assertion fails correctly when using NULL to ignore state.
     try {
@@ -492,7 +535,7 @@ public function testLegacyFieldAssertsWithNonTextfields() {
       $this->pass('assertNoFieldById failed correctly. The "edit-checkbox-disabled" field was found by ID using NULL value.');
     }
 
-    // Test the specific 'checked' assertions.
+    // Part 3 - Test the specific 'checked' assertions.
     $this->assertFieldChecked('edit-checkbox-enabled');
     $this->assertNoFieldChecked('edit-checkbox-disabled');