.../rest/tests/modules/rest_test/rest_test.module  | 17 ++++++++-------
 .../EntityResource/EntityResourceTestBase.php      | 24 ++++++++++++++++++----
 2 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/core/modules/rest/tests/modules/rest_test/rest_test.module b/core/modules/rest/tests/modules/rest_test/rest_test.module
index 197b82f..7ee3aa6 100644
--- a/core/modules/rest/tests/modules/rest_test/rest_test.module
+++ b/core/modules/rest/tests/modules/rest_test/rest_test.module
@@ -35,14 +35,13 @@ function rest_test_entity_field_access($operation, FieldDefinitionInterface $fie
 }
 
 /**
- * Implements hook_entity_base_field_info().
+ * Implements hook_entity_bundle_field_info_alter().
+ *
+ * @see \Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase::setUp()
+ * @todo Remove this in https://www.drupal.org/node/2905890.
  */
-function rest_test_entity_base_field_info(EntityTypeInterface $entity_type) {
-  $fields = [];
-  $fields['rest_test_validation'] = BaseFieldDefinition::create('string')
-    ->setLabel(t('REST test validation field'))
-    ->setDescription(t('A text field with some special validations attached used for testing purposes'))
-    ->addConstraint('rest_test_validation');
-
-  return $fields;
+function rest_test_entity_bundle_field_info_alter(&$fields, EntityTypeInterface $entity_type, $bundle) {
+  if (!empty($fields['rest_test_validation'])) {
+    $fields['rest_test_validation']->addConstraint('rest_test_validation', []);
+  }
 }
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
index 2354ccb..9517b62 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
@@ -180,12 +180,30 @@ public function setUp() {
         ->setTranslatable(FALSE)
         ->save();
 
-      // Reload entity so that it has the new field.
+      // Add field for testing validation.
+      // @see rest_test_entity_bundle_field_info_alter()
+      FieldStorageConfig::create([
+        'entity_type' => static::$entityTypeId,
+        'field_name' => 'rest_test_validation',
+        'type' => 'string',
+      ])
+        ->setCardinality(2)
+        ->save();
+      FieldConfig::create([
+        'entity_type' => static::$entityTypeId,
+        'field_name' => 'rest_test_validation',
+        'bundle' => $this->entity->bundle(),
+        'description' => 'A text field with some special validations attached used for testing purposes',
+      ])
+        ->setLabel('REST test validation field')
+        ->setTranslatable(FALSE)
+        ->save();
+
+      // Reload entity so that it has the new fields.
       $this->entity = $this->entityStorage->loadUnchanged($this->entity->id());
 
       // Set a default value on the field.
       $this->entity->set('field_rest_test', ['value' => 'All the faith he had had had had no effect on the outcome of his life.']);
-
       $this->entity->set('rest_test_validation', ['value' => 'allowed value']);
       $this->entity->save();
     }
@@ -471,7 +489,6 @@ public function testGet() {
         ]
       ];
     }
-
     static::recursiveKSort($expected);
     $actual = $this->serializer->decode((string) $response->getBody(), static::$format);
     static::recursiveKSort($actual);
@@ -578,7 +595,6 @@ public function testGet() {
       // ::formatExpectedTimestampValue() to generate the timestamp value. This
       // will take into account the above config setting.
       $expected = $this->getExpectedNormalizedEntity();
-
       $expected += [
         'rest_test_validation' => [
           [