diff --git a/core/modules/file/src/Tests/FileFieldWidgetTest.php b/core/modules/file/src/Tests/FileFieldWidgetTest.php
index f666527..e6cb08f 100644
--- a/core/modules/file/src/Tests/FileFieldWidgetTest.php
+++ b/core/modules/file/src/Tests/FileFieldWidgetTest.php
@@ -429,7 +429,7 @@ public function testWidgetValidation() {
       $name = 'files[' . $field_name . '_0]';
 
       // Check field is marked with expected attr for client-side validation.
-      $this->assertFieldByXPath('//input[@type="file" and @data-drupal-validate-extensions="[\"txt\"]"]', null, 'data-drupal-validate-extensions is present with expected value.');
+      $this->assertFieldByXPath('//input[@type="file" and @data-drupal-validate-extensions=\'["txt"]\']', NULL, 'data-drupal-validate-extensions is present with expected value.');
 
       // Upload file with incorrect extension, check for validation error.
       $edit[$name] = drupal_realpath($test_file_image->getFileUri());
diff --git a/core/modules/file/src/Tests/FileManagedFileElementTest.php b/core/modules/file/src/Tests/FileManagedFileElementTest.php
index a0c6cf3..b102e47 100644
--- a/core/modules/file/src/Tests/FileManagedFileElementTest.php
+++ b/core/modules/file/src/Tests/FileManagedFileElementTest.php
@@ -20,7 +20,7 @@ public function testManagedFile() {
 
     // Check that relevant data- attributes are present for validations
     $this->drupalGet('file/test/validation/extension');
-    $this->assertFieldByXPath('//input[@name="files[file]" and @data-drupal-validate-extensions="[\"txt\"]"]', NULL, 'The data-drupal-validate-extensions attribute is present with the expected value on the upload element.');
+    $this->assertFieldByXPath('//input[@name="files[file]" and @data-drupal-validate-extensions=\'["txt"]\']', NULL, 'The data-drupal-validate-extensions attribute is present with the expected value on the upload element.');
 
     // Perform the tests with all permutations of $form['#tree'],
     // $element['#extended'], and $element['#multiple'].
diff --git a/core/modules/image/src/Tests/ImageFieldDisplayTest.php b/core/modules/image/src/Tests/ImageFieldDisplayTest.php
index 868c586..9b2f873 100644
--- a/core/modules/image/src/Tests/ImageFieldDisplayTest.php
+++ b/core/modules/image/src/Tests/ImageFieldDisplayTest.php
@@ -328,10 +328,10 @@ public function testImageFieldSettings() {
     $this->assertNoFieldByXPath('//input[@id="edit-' . strtr($field_name, '_', '-') . '-2-upload"]', 'Upload field for second file not present after it is uploaded.');
 
     $this->assertTrue($this->cssSelect('input#edit-' . strtr($field_name, '_', '-') . '-3-upload[multiple=multiple]'), 'Third file field presented having multiple attribute');
-    $this->assertFieldByName('files[' . $field_name . '_3][]', null, 'Third file field has correct name');
+    $this->assertFieldByName('files[' . $field_name . '_3][]', NULL, 'Third file field has correct name');
     $this->assertTrue($this->cssSelect('input[id=edit-' . strtr($field_name, '_', '-') . '-3-upload][size=22]'), 'Third file field presented having correct size attribute');
     $this->assertTrue($this->cssSelect('input.js-form-file.form-file[id=edit-' . strtr($field_name, '_', '-') . '-3-upload]'), 'Third file field presented having correct css classes');
-    $this->assertFieldByXPath('//input[@id="edit-' . strtr($field_name, '_', '-') . '-3-upload"] and @data-drupal-validate-extensions="[\"txt\"]"]', NULL, 'The data-drupal-validate-extensions attribute is present with the expected value on the upload element.');
+    $this->assertFieldByXPath('//input[@id="edit-' . strtr($field_name, '_', '-') . '-3-upload"] and @data-drupal-validate-extensions=\'["txt"]\']', NULL, 'The data-drupal-validate-extensions attribute is present with the expected value on the upload element.');
   }
 
   /**