diff -u b/core/modules/rest/src/Tests/UpdateTest.php b/core/modules/rest/src/Tests/UpdateTest.php
--- b/core/modules/rest/src/Tests/UpdateTest.php
+++ b/core/modules/rest/src/Tests/UpdateTest.php
@@ -54,7 +54,7 @@
     $patch_entity = entity_create($entity_type, $patch_values);
     // We don't want to overwrite the UUID.
     unset($patch_entity->uuid);
-    // We don't want to overwrite the changed time.
+    // We cannot overwrite the changed time.
     unset($patch_entity->changed);
     $serialized = $serializer->serialize($patch_entity, $this->defaultFormat, $context);
 
@@ -147,6 +147,8 @@
     // Try to send invalid data to trigger the entity validation constraints.
     // Send a UUID that is too long.
     $entity->set('uuid', $this->randomMachineName(129));
+    // We cannot overwrite the changed time.
+    unset($entity->changed);
     $invalid_serialized = $serializer->serialize($entity, $this->defaultFormat, $context);
     $response = $this->httpRequest($entity->urlInfo(), 'PATCH', $invalid_serialized, $this->defaultMimeType);
     $this->assertResponse(422);
reverted:
--- b/core/modules/system/src/Tests/Entity/EntityChangedConstraintValidatorTest.php
+++ /dev/null
@@ -1,64 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\system\Tests\Entity\EntityChangedConstraintValidatorTest.
- */
-
-namespace Drupal\system\Tests\Entity;
-
-use Drupal\system\Tests\Entity\EntityUnitTestBase;
-use Drupal\system\Tests\TypedData;
-use Drupal\Core\TypedData\DataDefinition;
-use Drupal\entity_test\Entity\EntityTestChanged;
-
-/**
- * Tests validation constraints for EntityChangedConstraintValidator.
- *
- * @group Validation
- */
-class EntityChangedConstraintValidatorTest extends EntityUnitTestBase {
-
-  /**
-   * The typed data manager to use.
-   *
-   * @var \Drupal\Core\TypedData\TypedDataManager
-   */
-  protected $typedData;
-
-  public function setUp() {
-    parent::setUp();
-    $this->typedData = $this->container->get('typed_data_manager');
-  }
-
-  /**
-   * Tests the EntityChangedConstraintValidator.
-   */
-  public function testValidation() {
-    // Test the validation.
-    $account = $this->createUser();
-    $entity_test = entity_create('entity_test', array('user_id' => $account->id()));
-
-    $entity_test->save();
-    $violations = $entity_test->changed->validate();
-    $this->assertEqual($violations->count(), 0, 'Validation passed for correct value.');
-    // Set a changed date in the future.
-    $entity_test->set('changed', REQUEST_TIME + 100000);
-    // Run validation on the changed field.
-    $violations = $entity_test->changed->validate();
-    $this->assertEqual($violations->count(), 0, 'Validation passed for correct value.');
-
-    // Test the validation when an invalid value is passed.
-    // Set a changed date in the past.
-    $entity_test->set('changed', 433918800);
-    // Run validation on the changed field.
-    $violations = $entity_test->changed->validate();
-    $this->assertEqual($violations->count(), 1, 'Validation failed for incorrect value.');
-
-    // Make sure the information provided by a violation is correct.
-    $violation = $violations[0];
-    // The property path is 0 as the validator is being run on the field.
-    $this->assertEqual($violation->getPropertyPath(), '0');
-    $this->assertEqual($violation->getMessage(), t('The content has either been modified by another user, or you have already submitted modifications. As a result, your changes cannot be saved.'));
-  }
-}
only in patch2:
unchanged:
--- a/core/modules/rest/src/Tests/CreateTest.php
+++ b/core/modules/rest/src/Tests/CreateTest.php
@@ -58,7 +58,8 @@ public function testCreateResourceRestApiNotEnabled() {
     // Populate some entity properties before create the entity.
     $entity_values = $this->entityValues($entity_type);
     $entity = EntityTest::create($entity_values);
-
+    // We cannot overwrite the changed time.
+    unset($entity->changed);
     // Serialize the entity before the POST request.
     $serialized = $this->serializer->serialize($entity, $this->defaultFormat, ['account' => $account]);
 
only in patch2:
unchanged:
--- a/core/modules/rest/src/Tests/CsrfTest.php
+++ b/core/modules/rest/src/Tests/CsrfTest.php
@@ -54,6 +54,8 @@ protected function setUp() {
     $serializer = $this->container->get('serializer');
     $entity_values = $this->entityValues($this->testEntityType);
     $entity = entity_create($this->testEntityType, $entity_values);
+    // We cannot overwrite the changed time.
+    unset($entity->changed);
     $this->serialized = $serializer->serialize($entity, $this->defaultFormat);
   }