.../tests/src/Kernel/LinkItemSerializationTest.php |  7 ++---
 .../EntityTest/EntityTestMapItemNormalizerTest.php | 11 ++++----
 ...rTest.php => PropertylessMapNormalizerTest.php} | 10 ++++----
 .../src/Plugin/Field/FieldType/MapTestItem.php     | 30 ----------------------
 4 files changed, 14 insertions(+), 44 deletions(-)

diff --git a/core/modules/link/tests/src/Kernel/LinkItemSerializationTest.php b/core/modules/link/tests/src/Kernel/LinkItemSerializationTest.php
index 0804607..cd73ab1 100644
--- a/core/modules/link/tests/src/Kernel/LinkItemSerializationTest.php
+++ b/core/modules/link/tests/src/Kernel/LinkItemSerializationTest.php
@@ -17,9 +17,7 @@
 class LinkItemSerializationTest extends FieldKernelTestBase {
 
   /**
-   * Modules to enable.
-   *
-   * @var array
+   * {@inheritdoc}
    */
   public static $modules = ['link', 'serialization'];
 
@@ -28,6 +26,9 @@ class LinkItemSerializationTest extends FieldKernelTestBase {
    */
   protected $serializer;
 
+  /**
+   * {@inheritdoc}
+   */
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestMapItemNormalizerTest.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestMapItemNormalizerTest.php
index 194bce3..f57e799 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestMapItemNormalizerTest.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestMapItemNormalizerTest.php
@@ -7,8 +7,6 @@
 use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
 
 /**
- * Test that MapItem are correctly exposed in REST.
- *
  * @group rest
  */
 class EntityTestMapItemNormalizerTest extends EntityTestResourceTestBase {
@@ -20,6 +18,11 @@ class EntityTestMapItemNormalizerTest extends EntityTestResourceTestBase {
    */
   protected static $format = 'json';
 
+  /**
+   * The value to use for testing the "map" field.
+   *
+   * @var array
+   */
   protected static $mapValue = [
     'key1' => 'value',
     'key2' => 'no, val you',
@@ -29,7 +32,6 @@ class EntityTestMapItemNormalizerTest extends EntityTestResourceTestBase {
     ],
   ];
 
-
   /**
    * {@inheritdoc}
    */
@@ -40,9 +42,6 @@ class EntityTestMapItemNormalizerTest extends EntityTestResourceTestBase {
    */
   protected function getExpectedNormalizedEntity() {
     $expected = parent::getExpectedNormalizedEntity();
-    // The 'non_exposed_value' property in test field type will not return in
-    // normalization because setExposed(TRUE) was not called for this property.
-    // @see \Drupal\entity_test\Plugin\Field\FieldType\ExposedPropertyTestFieldItem::propertyDefinitions
     $expected['field_map'] = [
       static::$mapValue
     ];
diff --git a/core/modules/serialization/tests/src/Kernel/MapDataNormalizerTest.php b/core/modules/serialization/tests/src/Kernel/PropertylessMapNormalizerTest.php
similarity index 91%
rename from core/modules/serialization/tests/src/Kernel/MapDataNormalizerTest.php
rename to core/modules/serialization/tests/src/Kernel/PropertylessMapNormalizerTest.php
index 11e3353..8dad819 100644
--- a/core/modules/serialization/tests/src/Kernel/MapDataNormalizerTest.php
+++ b/core/modules/serialization/tests/src/Kernel/PropertylessMapNormalizerTest.php
@@ -9,12 +9,11 @@
 /**
  * @group typedData
  */
-class MapDataNormalizerTest extends KernelTestBase {
+class PropertylessMapNormalizerTest extends KernelTestBase {
 
   /**
    * {@inheritdoc}
    */
-
   public static $modules = ['system', 'serialization'];
 
   /**
@@ -120,9 +119,10 @@ protected function buildExampleTypedDataWithProperties() {
       ->setPropertyDefinition('key2', DataDefinition::create('string'))
       ->setPropertyDefinition('key3', DataDefinition::create('integer'))
       ->setPropertyDefinition('key4', MapDataDefinition::create()
-      ->setPropertyDefinition(0, DataDefinition::create('boolean'))
-      ->setPropertyDefinition(1, DataDefinition::create('string'))
-      ->setPropertyDefinition('key7', DataDefinition::create('string'))
+        ->setPropertyDefinition(0, DataDefinition::create('boolean'))
+        ->setPropertyDefinition(1, DataDefinition::create('string'))
+        ->setPropertyDefinition('key7', DataDefinition::create('string')
+      )
     );
 
     $typed_data = $this->typedDataManager->create(
diff --git a/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/MapTestItem.php b/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/MapTestItem.php
deleted file mode 100644
index dfb1295..0000000
--- a/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/MapTestItem.php
+++ /dev/null
@@ -1,30 +0,0 @@
-<?php
-
-namespace Drupal\entity_test\Plugin\Field\FieldType;
-
-use Drupal\Core\Field\FieldItemBase;
-use Drupal\Core\Field\FieldStorageDefinitionInterface;
-use Drupal\Core\Field\Plugin\Field\FieldType\MapItem;
-use Drupal\Core\TypedData\MapDataDefinition;
-
-/**
- * Defines the 'map_test' field type.
- *
- * @FieldType(
- *   id = "map_test",
- *   label = @Translation("Map Test"),
- *   description = @Translation("Another dummy field type."),
- * )
- */
-class MapTestItem extends MapItem {
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
-    return [
-      'value' => MapDataDefinition::create()->setLabel(t('Freeform')),
-    ];
-  }
-
-}