diff --git a/composer.lock b/composer.lock
index ddaa66ee82..be64d24bdf 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4194,23 +4194,23 @@
         },
         {
             "name": "symfony/phpunit-bridge",
-            "version": "v3.2.8",
+            "version": "dev-master",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/phpunit-bridge.git",
-                "reference": "00916603c524b8048906de460b7ea0dfa1651281"
+                "reference": "884e6aac4e6a07d427187a35194821cbc2a0c82c"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/phpunit-bridge/zipball/00916603c524b8048906de460b7ea0dfa1651281",
-                "reference": "00916603c524b8048906de460b7ea0dfa1651281",
+                "url": "https://api.github.com/repos/symfony/phpunit-bridge/zipball/884e6aac4e6a07d427187a35194821cbc2a0c82c",
+                "reference": "884e6aac4e6a07d427187a35194821cbc2a0c82c",
                 "shasum": ""
             },
             "require": {
                 "php": ">=5.3.3"
             },
             "conflict": {
-                "phpunit/phpunit": ">=6.0"
+                "phpunit/phpunit": "<4.8.35|<5.4.3,>=5.0"
             },
             "suggest": {
                 "ext-zip": "Zip support is required when using bin/simple-phpunit",
@@ -4222,7 +4222,7 @@
             "type": "symfony-bridge",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "3.2-dev"
+                    "dev-master": "4.0-dev"
                 }
             },
             "autoload": {
@@ -4252,13 +4252,14 @@
             ],
             "description": "Symfony PHPUnit Bridge",
             "homepage": "https://symfony.com",
-            "time": "2017-04-12T14:13:17+00:00"
+            "time": "2017-10-13T14:15:21+00:00"
         }
     ],
     "aliases": [],
     "minimum-stability": "dev",
     "stability-flags": {
-        "behat/mink": 20
+        "behat/mink": 20,
+        "symfony/phpunit-bridge": 20
     },
     "prefer-stable": true,
     "prefer-lowest": false,
diff --git a/core/composer.json b/core/composer.json
index c802e5d6ee..46c32fb3d3 100644
--- a/core/composer.json
+++ b/core/composer.json
@@ -18,7 +18,7 @@
         "symfony/process": "~3.2.8",
         "symfony/polyfill-iconv": "^1.0",
         "symfony/yaml": "~3.2.8",
-        "twig/twig": "^1.35.0",
+        "twig/twig": "^1.23.1",
         "doctrine/common": "^2.5",
         "doctrine/annotations": "^1.2",
         "guzzlehttp/guzzle": "^6.2.1",
@@ -47,7 +47,7 @@
         "phpunit/phpunit": ">=4.8.35 <5",
         "phpspec/prophecy": "^1.4",
         "symfony/css-selector": "~3.2.8",
-        "symfony/phpunit-bridge": "~3.2.8"
+        "symfony/phpunit-bridge": "dev-master"
     },
     "replace": {
         "drupal/action": "self.version",
diff --git a/core/modules/system/tests/modules/deprecation_test/deprecation_test.module b/core/modules/system/tests/modules/deprecation_test/deprecation_test.module
new file mode 100644
index 0000000000..fd1092a3c6
--- /dev/null
+++ b/core/modules/system/tests/modules/deprecation_test/deprecation_test.module
@@ -0,0 +1,15 @@
+<?php
+
+/**
+ * A deprecated function.
+ *
+ * @return string
+ *   A known return value of 'known_return_value'.
+ *
+ * @deprecated in Drupal 8.4.x. Might be removed before Drupal 9.0.0. This is
+ *   the deprecation message for deprecated_test_function().
+ */
+function deprecation_test_function() {
+  @trigger_error('This is the deprecation message for deprecation_test_function().', E_USER_DEPRECATED);
+  return 'known_return_value';
+}
diff --git a/core/modules/system/tests/modules/deprecation_test/deprecation_test.routing.yml b/core/modules/system/tests/modules/deprecation_test/deprecation_test.routing.yml
new file mode 100644
index 0000000000..3ef71b806f
--- /dev/null
+++ b/core/modules/system/tests/modules/deprecation_test/deprecation_test.routing.yml
@@ -0,0 +1,6 @@
+deprecation_test.route:
+  path: '/this-calls-a-deprecated-method'
+  defaults:
+    _controller: \Drupal\deprecation_test\DeprecatedController::deprecatedMethod
+  requirements:
+    _access: 'TRUE'
diff --git a/core/modules/system/tests/modules/deprecation_test/src/DeprecatedController.php b/core/modules/system/tests/modules/deprecation_test/src/DeprecatedController.php
new file mode 100644
index 0000000000..44cf330cc8
--- /dev/null
+++ b/core/modules/system/tests/modules/deprecation_test/src/DeprecatedController.php
@@ -0,0 +1,22 @@
+<?php
+
+namespace Drupal\deprecation_test;
+
+/**
+ * Defines a controller that calls a deprecated method.
+ */
+class DeprecatedController {
+
+  /**
+   * Controller callback.
+   *
+   * @return array
+   *   Render array.
+   */
+  public function deprecatedMethod() {
+    return [
+      '#markup' => deprecation_test_function(),
+    ];
+  }
+
+}
diff --git a/core/tests/Drupal/FunctionalTests/Core/Test/PhpUnitBridgeTest.php b/core/tests/Drupal/FunctionalTests/Core/Test/PhpUnitBridgeTest.php
new file mode 100644
index 0000000000..6cdb31c103
--- /dev/null
+++ b/core/tests/Drupal/FunctionalTests/Core/Test/PhpUnitBridgeTest.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace Drupal\FunctionalTests\Core\Test;
+
+use Drupal\Core\Url;
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests Drupal's integration with Symfony PHPUnit Bridge.
+ *
+ * @group Test
+ * @group legacy
+ */
+class PhpUnitBridgeTest extends BrowserTestBase {
+
+  protected static $modules = ['deprecation_test'];
+
+  /**
+   * @expectedDeprecation This is the deprecation message for deprecation_test_function().
+   */
+  public function testSilencedError() {
+    $this->assertEquals('known_return_value', deprecation_test_function());
+  }
+
+  /**
+   * @expectedDeprecation This is the deprecation message for deprecated_test_function().
+   */
+  public function testErrorOnSiteUnderTest() {
+    $this->drupalGet(Url::fromRoute('deprecation_test.route'));
+  }
+
+}
diff --git a/core/tests/Drupal/KernelTests/Core/Test/PhpUnitBridgeTest.php b/core/tests/Drupal/KernelTests/Core/Test/PhpUnitBridgeTest.php
new file mode 100644
index 0000000000..d82a37b906
--- /dev/null
+++ b/core/tests/Drupal/KernelTests/Core/Test/PhpUnitBridgeTest.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace Drupal\KernelTests\Core\Test;
+
+use Drupal\KernelTests\KernelTestBase;
+use Drupal\deprecation_test\Deprecation\FixtureDeprecatedClass;
+
+/**
+ * Test how kernel tests interact with deprecation errors.
+ *
+ * @group Test
+ * @group legacy
+ */
+class PhpUnitBridgeTest extends KernelTestBase {
+
+  public static $modules = ['deprecation_test'];
+
+  /**
+   * @expectedDeprecation Drupal\deprecation_test\Deprecation\FixtureDeprecatedClass is deprecated.
+   */
+  public function testDeprecatedClass() {
+    $deprecated = new FixtureDeprecatedClass();
+    $this->assertEquals('test', $deprecated->testFunction());
+  }
+
+  /**
+   * @expectedDeprecation This is the deprecation message for deprecation_test_function().
+   */
+  public function testDeprecatedFunction() {
+    $this->assertEquals('known_return_value', \deprecation_test_function());
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Core/Test/PhpUnitBridgeIsolatedTest.php b/core/tests/Drupal/Tests/Core/Test/PhpUnitBridgeIsolatedTest.php
new file mode 100644
index 0000000000..72806b44c3
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Test/PhpUnitBridgeIsolatedTest.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace Drupal\Tests\Core\Test;
+
+use Drupal\Tests\UnitTestCase;
+use Drupal\deprecation_test\Deprecation\FixtureDeprecatedClass;
+
+/**
+ * Test how unit tests interact with deprecation errors in process isolation.
+ *
+ * @runTestsInSeparateProcesses
+ *
+ * @group Test
+ * @group legacy
+ */
+class PhpUnitBridgeIsolatedTest extends UnitTestCase {
+
+  /**
+   * @expectedDeprecation Drupal\deprecation_test\Deprecation\FixtureDeprecatedClass is deprecated.
+   */
+  public function testDeprecatedClass() {
+    $deprecated = new FixtureDeprecatedClass();
+    $this->assertEquals('test', $deprecated->testFunction());
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Core/Test/PhpUnitBridgeTest.php b/core/tests/Drupal/Tests/Core/Test/PhpUnitBridgeTest.php
new file mode 100644
index 0000000000..73ba0de167
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Test/PhpUnitBridgeTest.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace Drupal\Tests\Core\Test;
+
+use Drupal\Tests\UnitTestCase;
+use Drupal\deprecation_test\Deprecation\FixtureDeprecatedClass;
+
+/**
+ * Test how unit tests interact with deprecation errors.
+ *
+ * @group Test
+ * @group legacy
+ */
+class PhpUnitBridgeTest extends UnitTestCase {
+
+  /**
+   * @expectedDeprecation Drupal\deprecation_test\Deprecation\FixtureDeprecatedClass is deprecated.
+   */
+  public function testDeprecatedClass() {
+    $deprecated = new FixtureDeprecatedClass();
+    $this->assertEquals('test', $deprecated->testFunction());
+  }
+
+  public function testDeprecatedFunction() {
+    $this->markTestIncomplete('Modules are not loaded for unit tests, so deprecated_test_function() will not be available.');
+    $this->assertEquals('known_return_value', \deprecation_test_function());
+  }
+
+}