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..b73a8870cb
--- /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 deprecated_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..3de3982046
--- /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\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());
+  }
+
+}