diff --git a/core/modules/file/tests/src/Functional/FileFieldDisplayTest.php b/core/modules/file/tests/src/Functional/FileFieldDisplayTest.php
index 922985cb4e3..72d150e70f6 100644
--- a/core/modules/file/tests/src/Functional/FileFieldDisplayTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldDisplayTest.php
@@ -115,7 +115,7 @@ class FileFieldDisplayTest extends FileFieldTestBase {
     $this->assertSession()->responseContains($field_name . '[1][description]', 'Description of second file appears as expected.');
 
     // Check that the file fields don't contain duplicate HTML IDs.
-    $this->assertNoDuplicateIds();
+    $this->assertSession()->pageContainsNoDuplicateId();
   }
 
   /**
@@ -229,32 +229,4 @@ class FileFieldDisplayTest extends FileFieldTestBase {
     $this->assertFieldByXPath('//a[@href="' . $node->{$field_name}->entity->createFileUrl(FALSE) . '"]', $description);
   }
 
-  /**
-   * Asserts that each HTML ID is used for just a single element on the page.
-   *
-   * @param string $message
-   *   (optional) A message to display with the assertion.
-   */
-  protected function assertNoDuplicateIds($message = '') {
-    $args = ['@url' => $this->getUrl()];
-
-    if (!$elements = $this->xpath('//*[@id]')) {
-      $this->fail(new FormattableMarkup('The page @url contains no HTML IDs.', $args));
-      return;
-    }
-
-    $message = $message ?: new FormattableMarkup('The page @url does not contain duplicate HTML IDs', $args);
-
-    $seen_ids = [];
-    foreach ($elements as $element) {
-      $id = $element->getAttribute('id');
-      if (isset($seen_ids[$id])) {
-        $this->fail($message);
-        return;
-      }
-      $seen_ids[$id] = TRUE;
-    }
-    $this->assertTrue(TRUE, $message);
-  }
-
 }
diff --git a/core/modules/system/tests/modules/test_page_test/src/Controller/Test.php b/core/modules/system/tests/modules/test_page_test/src/Controller/Test.php
index 08ff6155105..c59002baf50 100644
--- a/core/modules/system/tests/modules/test_page_test/src/Controller/Test.php
+++ b/core/modules/system/tests/modules/test_page_test/src/Controller/Test.php
@@ -155,6 +155,56 @@ class Test {
     return new RedirectResponse(Url::fromRoute('test_page_test.test_page', [], ['absolute' => TRUE])->toString(), 302);
   }
 
+  /**
+   * Returns a page render array with 2 elements with the same HTML IDs.
+   *
+   * @return array
+   *   A render array as expected by
+   *   \Drupal\Core\Render\RendererInterface::render().
+   */
+  public function renderPageWithDuplicateIds() {
+    return [
+      '#type' => 'container',
+      'title' => [
+        '#type' => 'html_tag',
+        '#tag' => 'h1',
+        '#value' => 'Hello',
+        '#attributes' => ['id' => 'page-element'],
+      ],
+      'description' => [
+        '#type' => 'html_tag',
+        '#tag' => 'h2',
+        '#value' => 'World',
+        '#attributes' => ['id' => 'page-element'],
+      ],
+    ];
+  }
+
+  /**
+   * Returns a page render array with 2 elements with the unique HTML IDs.
+   *
+   * @return array
+   *   A render array as expected by
+   *   \Drupal\Core\Render\RendererInterface::render().
+   */
+  public function renderPageWithoutDuplicateIds() {
+    return [
+      '#type' => 'container',
+      'title' => [
+        '#type' => 'html_tag',
+        '#tag' => 'h1',
+        '#value' => 'Hello',
+        '#attributes' => ['id' => 'page-element-title'],
+      ],
+      'description' => [
+        '#type' => 'html_tag',
+        '#tag' => 'h2',
+        '#value' => 'World',
+        '#attributes' => ['id' => 'page-element-description'],
+      ],
+    ];
+  }
+
   /**
    * Returns a page while triggering deprecation notices.
    */
diff --git a/core/modules/system/tests/modules/test_page_test/test_page_test.routing.yml b/core/modules/system/tests/modules/test_page_test/test_page_test.routing.yml
index 336f6c704ba..2f44e099db6 100644
--- a/core/modules/system/tests/modules/test_page_test/test_page_test.routing.yml
+++ b/core/modules/system/tests/modules/test_page_test/test_page_test.routing.yml
@@ -115,6 +115,20 @@ test_page_test.meta_refresh:
   requirements:
     _access: 'TRUE'
 
+test_page_test.page_with_duplicate_ids:
+  path: '/test-page-with-duplicate-ids'
+  defaults:
+    _controller: '\Drupal\test_page_test\Controller\Test::renderPageWithDuplicateIds'
+  requirements:
+    _access: 'TRUE'
+
+test_page_test.page_without_duplicate_ids:
+  path: '/test-page-without-duplicate-ids'
+  defaults:
+    _controller: '\Drupal\test_page_test\Controller\Test::renderPageWithoutDuplicateIds'
+  requirements:
+    _access: 'TRUE'
+
 test_page_test.deprecations:
   path: '/test-deprecations'
   defaults:
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MultiFormTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MultiFormTest.php
index 8b52d89a795..680cbb0ef31 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MultiFormTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MultiFormTest.php
@@ -2,7 +2,6 @@
 
 namespace Drupal\FunctionalJavascriptTests\Ajax;
 
-use Drupal\Component\Render\FormattableMarkup;
 use Drupal\Core\Field\FieldStorageDefinitionInterface;
 use Drupal\field\Entity\FieldConfig;
 use Drupal\field\Entity\FieldStorageConfig;
@@ -88,7 +87,7 @@ class MultiFormTest extends WebDriverTestBase {
       $this->assertFieldsByValue($field->find('xpath', '.' . $button_xpath_suffix), NULL, 'Found the "add more" button on the initial page.');
     }
 
-    $this->assertNoDuplicateIds();
+    $this->assertSession()->pageContainsNoDuplicateId();
 
     // Submit the "add more" button of each form twice. After each corresponding
     // page update, ensure the same as above.
@@ -108,37 +107,9 @@ class MultiFormTest extends WebDriverTestBase {
         $field = $page_updated->findAll('xpath', '.' . $field_xpath);
         $this->assertCount($i + 2, $field[0]->find('xpath', '.' . $field_items_xpath_suffix), 'Found the correct number of field items after an AJAX submission.');
         $this->assertFieldsByValue($field[0]->find('xpath', '.' . $button_xpath_suffix), NULL, 'Found the "add more" button after an AJAX submission.');
-        $this->assertNoDuplicateIds();
+        $this->assertSession()->pageContainsNoDuplicateId();
       }
     }
   }
 
-  /**
-   * Asserts that each HTML ID is used for just a single element on the page.
-   *
-   * @param string $message
-   *   (optional) A message to display with the assertion.
-   */
-  protected function assertNoDuplicateIds($message = '') {
-    $args = ['@url' => $this->getUrl()];
-
-    if (!$elements = $this->xpath('//*[@id]')) {
-      $this->fail(new FormattableMarkup('The page @url contains no HTML IDs.', $args));
-      return;
-    }
-
-    $message = $message ?: new FormattableMarkup('The page @url does not contain duplicate HTML IDs', $args);
-
-    $seen_ids = [];
-    foreach ($elements as $element) {
-      $id = $element->getAttribute('id');
-      if (isset($seen_ids[$id])) {
-        $this->fail($message);
-        return;
-      }
-      $seen_ids[$id] = TRUE;
-    }
-    $this->assertTrue(TRUE, $message);
-  }
-
 }
diff --git a/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php b/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
index d6d8e442462..5ff8d75f48f 100644
--- a/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
+++ b/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
@@ -770,6 +770,22 @@ class BrowserTestBaseTest extends BrowserTestBase {
     $this->assertSession()->statusCodeEquals(403);
   }
 
+  /**
+   * Tests pageContainsNoDuplicateId() functionality.
+   *
+   * @see \Drupal\Tests\WebAssert::pageContainsNoDuplicateId()
+   */
+  public function testPageContainsNoDuplicateId() {
+    $assert_session = $this->assertSession();
+    $this->drupalGet(Url::fromRoute('test_page_test.page_without_duplicate_ids'));
+    $assert_session->pageContainsNoDuplicateId();
+
+    $this->drupalGet(Url::fromRoute('test_page_test.page_with_duplicate_ids'));
+    $this->expectException(ExpectationException::class);
+    $this->expectExceptionMessage('The page contains a duplicate HTML ID "page-element".');
+    $assert_session->pageContainsNoDuplicateId();
+  }
+
   /**
    * Tests assertEscaped() and assertUnescaped().
    *
diff --git a/core/tests/Drupal/Tests/WebAssert.php b/core/tests/Drupal/Tests/WebAssert.php
index 7b296263ae4..e296077c217 100644
--- a/core/tests/Drupal/Tests/WebAssert.php
+++ b/core/tests/Drupal/Tests/WebAssert.php
@@ -626,4 +626,20 @@ class WebAssert extends MinkWebAssert {
     throw new ResponseTextException($message, $this->session->getDriver());
   }
 
+  /**
+   * Asserts that each HTML ID is used for just a single element on the page.
+   *
+   * @throws \Behat\Mink\Exception\ExpectationException
+   */
+  public function pageContainsNoDuplicateId() {
+    $seen_ids = [];
+    foreach ($this->session->getPage()->findAll('xpath', '//*[@id]') as $element) {
+      $id = $element->getAttribute('id');
+      if (isset($seen_ids[$id])) {
+        throw new ExpectationException(sprintf('The page contains a duplicate HTML ID "%s".', $id), $this->session->getDriver());
+      }
+      $seen_ids[$id] = TRUE;
+    }
+  }
+
 }