diff --git a/composer.lock b/composer.lock
index 4260388..9d589c8 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4173,6 +4173,68 @@
             "description": "Symfony DomCrawler Component",
             "homepage": "https://symfony.com",
             "time": "2017-02-21T09:12:04+00:00"
+        },
+        {
+            "name": "symfony/phpunit-bridge",
+            "version": "v3.2.8",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/phpunit-bridge.git",
+                "reference": "00916603c524b8048906de460b7ea0dfa1651281"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/phpunit-bridge/zipball/00916603c524b8048906de460b7ea0dfa1651281",
+                "reference": "00916603c524b8048906de460b7ea0dfa1651281",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.3.3"
+            },
+            "conflict": {
+                "phpunit/phpunit": ">=6.0"
+            },
+            "suggest": {
+                "ext-zip": "Zip support is required when using bin/simple-phpunit",
+                "symfony/debug": "For tracking deprecated interfaces usages at runtime with DebugClassLoader"
+            },
+            "bin": [
+                "bin/simple-phpunit"
+            ],
+            "type": "symfony-bridge",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "3.2-dev"
+                }
+            },
+            "autoload": {
+                "files": [
+                    "bootstrap.php"
+                ],
+                "psr-4": {
+                    "Symfony\\Bridge\\PhpUnit\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Symfony PHPUnit Bridge",
+            "homepage": "https://symfony.com",
+            "time": "2017-04-12T14:13:17+00:00"
         }
     ],
     "aliases": [],
diff --git a/core/composer.json b/core/composer.json
index 4f328ce..0be4b81 100644
--- a/core/composer.json
+++ b/core/composer.json
@@ -45,7 +45,8 @@
         "jcalderonzumba/mink-phantomjs-driver": "~0.3.1",
         "mikey179/vfsStream": "~1.2",
         "phpunit/phpunit": ">=4.8.35 <5",
-        "symfony/css-selector": "3.2.6"
+        "symfony/css-selector": "3.2.6",
+        "symfony/phpunit-bridge": "^3.2"
     },
     "replace": {
         "drupal/action": "self.version",
diff --git a/core/lib/Drupal/Component/Serialization/YamlSymfony.php b/core/lib/Drupal/Component/Serialization/YamlSymfony.php
index 390178f..d35e09c 100644
--- a/core/lib/Drupal/Component/Serialization/YamlSymfony.php
+++ b/core/lib/Drupal/Component/Serialization/YamlSymfony.php
@@ -17,8 +17,8 @@ class YamlSymfony implements SerializationInterface {
    */
   public static function encode($data) {
     try {
-      $yaml = new Dumper();
-      $yaml->setIndentation(2);
+      // Set the indentation to 2 to match Drupal's coding standards.
+      $yaml = new Dumper(2);
       return $yaml->dump($data, PHP_INT_MAX, 0, SymfonyYaml::DUMP_EXCEPTION_ON_INVALID_TYPE);
     }
     catch (\Exception $e) {
diff --git a/core/tests/Drupal/Tests/Core/Controller/ControllerResolverTest.php b/core/tests/Drupal/Tests/Core/Controller/ControllerResolverTest.php
index 28040a6..0b7aa25 100644
--- a/core/tests/Drupal/Tests/Core/Controller/ControllerResolverTest.php
+++ b/core/tests/Drupal/Tests/Core/Controller/ControllerResolverTest.php
@@ -70,6 +70,8 @@ protected function setUp() {
    *
    * @see \Drupal\Core\Controller\ControllerResolver::getArguments()
    * @see \Drupal\Core\Controller\ControllerResolver::doGetArguments()
+   *
+   * @group legacy
    */
   public function testGetArguments() {
     $controller = function(EntityInterface $entity, $user, RouteMatchInterface $route_match, ServerRequestInterface $psr_7) {
@@ -220,6 +222,8 @@ protected function assertCallableController($controller, $class, $output) {
    *
    * @covers ::getArguments
    * @covers ::doGetArguments
+   *
+   * @group legacy
    */
   public function testGetArgumentsWithRouteMatchAndRequest() {
     $request = Request::create('/test');
@@ -233,6 +237,8 @@ public function testGetArgumentsWithRouteMatchAndRequest() {
    *
    * @covers ::getArguments
    * @covers ::doGetArguments
+   *
+   * @group legacy
    */
   public function testGetArgumentsWithRouteMatchAndPsr7Request() {
     $request = Request::create('/test');