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 24a9bdb..98ddc7c 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/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php b/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
index 3689ddd..3ac6ba2 100644
--- a/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
+++ b/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
@@ -334,9 +334,9 @@ public function testLegacyFieldAssertsWithTextfields() {
   }
 
   /**
-   * Tests legacy field asserts on other types of field.
+   * Tests legacy field asserts for options field type.
    */
-  public function testLegacyFieldAssertsWithNonTextfields() {
+  public function testLegacyFieldAssertsWithOptions() {
     $this->drupalGet('test-field-xpath');
 
     // Option field type.
@@ -383,8 +383,14 @@ public function testLegacyFieldAssertsWithNonTextfields() {
     catch (\PHPUnit_Framework_ExpectationFailedException $e) {
       $this->pass($e->getMessage());
     }
+  }
+
+  /**
+   * Tests legacy field asserts for button field type.
+   */
+  public function testLegacyFieldAssertsWithButton() {
+    $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.
@@ -407,7 +413,26 @@ 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 testLegacyFieldAssertsWithCheckbox() {
+    $this->drupalGet('test-field-xpath');
+
     // 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);
@@ -415,6 +440,19 @@ public function testLegacyFieldAssertsWithNonTextfields() {
     $this->assertNoFieldByName('checkbox_enabled', FALSE);
     $this->assertNoFieldByName('checkbox_disabled', TRUE);
 
+    // Test with an empty string value for a checkbox, the value should be
+    // ignored.
+    $this->assertFieldByName('checkbox_disabled', '');
+    $this->assertFieldByName('checkbox_enabled', '');
+
+  }
+
+  /**
+   * Tests legacy field asserts for checkbox field type.
+   */
+  public function testLegacyFieldAssertsWithCheckboxTempPartTwo() {
+    $this->drupalGet('test-field-xpath');
+
     // Test that checkboxes are found by name when using NULL to ignore the
     // 'checked' state.
     $this->assertFieldByName('checkbox_enabled', NULL);
@@ -426,6 +464,10 @@ public function testLegacyFieldAssertsWithNonTextfields() {
     $this->assertFieldById('edit-checkbox-disabled', FALSE);
     $this->assertNoFieldById('edit-checkbox-enabled', FALSE);
     $this->assertNoFieldById('edit-checkbox-disabled', TRUE);
+    
+    // Test that we have full legacy support by passing an empty string.
+    $this->assertFieldById('edit-checkbox-disabled', '');
+    $this->assertFieldById('edit-checkbox-enabled', '');
 
     // Test that checkboxes are found by by ID, when using NULL to ignore the
     // 'checked' state.