diff --git a/core/modules/rest/src/Plugin/rest/resource/UserRegistrationResource.php b/core/modules/rest/src/Plugin/rest/resource/UserRegistrationResource.php
index 545516a..762e2f5 100644
--- a/core/modules/rest/src/Plugin/rest/resource/UserRegistrationResource.php
+++ b/core/modules/rest/src/Plugin/rest/resource/UserRegistrationResource.php
@@ -169,7 +169,7 @@ public function routes() {
 
     // Restrict the incoming HTTP Content-type header to the known serialization
     // formats.
-    $route->addRequirements(['_content_type_format' => implode('|', $this->serializerFormats)]));
+    $route->addRequirements(['_content_type_format' => implode('|', $this->serializerFormats)]);
     $collection->add("$this->pluginId", $route);
 
     return $collection;
diff --git a/core/modules/rest/tests/src/Unit/UserRegistrationResourceTest.php b/core/modules/rest/tests/src/Unit/UserRegistrationResourceTest.php
index 2facc31..6ac54f0 100644
--- a/core/modules/rest/tests/src/Unit/UserRegistrationResourceTest.php
+++ b/core/modules/rest/tests/src/Unit/UserRegistrationResourceTest.php
@@ -149,6 +149,8 @@ public function testValidate() {
   }
 
   /**
+   * Tests that error validation is thrown as expected.
+   *
    * @expectedException \Symfony\Component\HttpKernel\Exception\HttpException
    * @expectedException UserRegistrationResourceTest::ERROR_MESSAGE
    */
@@ -191,11 +193,13 @@ public function testFailedValidate() {
       ->will($this->returnValue($violations));
 
     $method = $this->getProtectedMethod('validate');
-    // No exception is thrown.
+
     $method->invoke($this->testClass, $entity);
   }
 
   /**
+   * Tests that an exception is thrown when no data provided for the account.
+   *
    * @expectedException \Symfony\Component\HttpKernel\Exception\BadRequestHttpException
    * @expectedExceptionMessage No user account data for registration received.
    */
@@ -204,8 +208,10 @@ public function testEmptyPost() {
   }
 
   /**
+   * Tests that only new user accounts can be registered.
+   *
    * @expectedException \Symfony\Component\HttpKernel\Exception\BadRequestHttpException
-   * @expectedExceptionMessage Only new user accounts can be registered.
+   * @expectedExceptionMessage An ID has been set and only new user accounts can be registered.
    */
   public function testExistedEntityPost() {
     $entity = $this->getMockBuilder(User::class)
@@ -220,6 +226,8 @@ public function testExistedEntityPost() {
   }
 
   /**
+   * Tests that admin permissions are required to register a user account.
+   *
    * @expectedException \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException
    * @expectedExceptionMessage Only administrators can register users.
    */
@@ -245,6 +253,8 @@ public function testRegistrationAdminOnlyPost() {
   }
 
   /**
+   * Tests that only anonymous users can register users.
+   *
    * @expectedException \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException
    * @expectedExceptionMessage Only anonymous users can register users.
    */
@@ -267,6 +277,8 @@ public function testRegistrationAnonymousOnlyPost() {
   }
 
   /**
+   * Tests access denied on creating field.
+   *
    * @expectedException \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException
    * @expectedExceptionMessage Access denied on creating field 'test_field'.
    */