.../src/Normalizer/StringNormalizer.php                    |  3 +++
 .../src/Normalizer/StringNormalizer.php                    |  3 +++
 tests/src/Functional/ExternalNormalizersTest.php           | 14 ++++++++++----
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/tests/modules/jsonapi_test_data_type/src/Normalizer/StringNormalizer.php b/tests/modules/jsonapi_test_data_type/src/Normalizer/StringNormalizer.php
index 95b5eff..abb6610 100644
--- a/tests/modules/jsonapi_test_data_type/src/Normalizer/StringNormalizer.php
+++ b/tests/modules/jsonapi_test_data_type/src/Normalizer/StringNormalizer.php
@@ -5,6 +5,9 @@ namespace Drupal\jsonapi_test_data_type\Normalizer;
 use Drupal\Core\TypedData\Plugin\DataType\StringData;
 use Drupal\serialization\Normalizer\NormalizerBase;
 
+/**
+ * Normalizes string data, with a twist: it replaces 'super' with 'NOT'.
+ */
 class StringNormalizer extends NormalizerBase {
 
   /**
diff --git a/tests/modules/jsonapi_test_field_type/src/Normalizer/StringNormalizer.php b/tests/modules/jsonapi_test_field_type/src/Normalizer/StringNormalizer.php
index 59c8ee7..0376ca6 100644
--- a/tests/modules/jsonapi_test_field_type/src/Normalizer/StringNormalizer.php
+++ b/tests/modules/jsonapi_test_field_type/src/Normalizer/StringNormalizer.php
@@ -5,6 +5,9 @@ namespace Drupal\jsonapi_test_field_type\Normalizer;
 use Drupal\Core\Field\Plugin\Field\FieldType\StringItem;
 use Drupal\serialization\Normalizer\FieldItemNormalizer;
 
+/**
+ * Normalizes string fields, with a twist: it replaces 'super' with 'NOT'.
+ */
 class StringNormalizer extends FieldItemNormalizer {
 
   /**
diff --git a/tests/src/Functional/ExternalNormalizersTest.php b/tests/src/Functional/ExternalNormalizersTest.php
index 2138a38..dcd99c1 100644
--- a/tests/src/Functional/ExternalNormalizersTest.php
+++ b/tests/src/Functional/ExternalNormalizersTest.php
@@ -117,7 +117,7 @@ class ExternalNormalizersTest extends BrowserTestBase {
 
     // Asserts that this does NOT affect the JSON API normalization.
     // @todo Remove line below in favor of commented line in https://www.drupal.org/project/jsonapi/issues/2878463.
-    $url = Url::fromRoute('jsonapi.entity_test--entity_test.individual', ['entity_test'=> $this->entity->uuid()]);
+    $url = Url::fromRoute('jsonapi.entity_test--entity_test.individual', ['entity_test' => $this->entity->uuid()]);
     /* $url = $this->entity->toUrl('jsonapi'); */
     $client = $this->getSession()->getDriver()->getClient()->getClient();
     $response = $client->request('GET', $url->setAbsolute(TRUE)->toString());
@@ -125,19 +125,25 @@ class ExternalNormalizersTest extends BrowserTestBase {
     $this->assertSame($expected_value_jsonapi_normalization, $document['data']['attributes']['field_test']);
   }
 
+  /**
+   * Data provider.
+   *
+   * @return array
+   *   Test cases.
+   */
   public function providerTestFormatAgnosticNormalizers() {
     return [
       'Format-agnostic @FieldType-level normalizers SHOULD NOT be able to affect the JSON API normalization' => [
         // \Drupal\jsonapi_test_field_type\Normalizer\StringNormalizer::normalize()
         'jsonapi_test_field_type',
-        static::VALUE_ORIGINAL
+        static::VALUE_ORIGINAL,
       ],
       'Format-agnostic @DataType-level normalizers SHOULD be able to affect the JSON API normalization' => [
         // \Drupal\jsonapi_test_field_type\Normalizer\StringNormalizer::normalize()
         'jsonapi_test_data_type',
-        static::VALUE_OVERRIDDEN
+        static::VALUE_OVERRIDDEN,
       ],
     ];
   }
 
-}
\ No newline at end of file
+}