diff --git a/core/modules/system/tests/modules/plugin_test/src/Plugin/MockBlockManager.php b/core/modules/system/tests/modules/plugin_test/src/Plugin/MockBlockManager.php
index aebb473..db4a052 100644
--- a/core/modules/system/tests/modules/plugin_test/src/Plugin/MockBlockManager.php
+++ b/core/modules/system/tests/modules/plugin_test/src/Plugin/MockBlockManager.php
@@ -35,6 +35,7 @@ public function __construct() {
 
     // A simple plugin: the user login block.
     $this->discovery->setDefinition('user_login', array(
+      'id' => 'user_login',
       'label' => t('User login'),
       'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockUserLoginBlock',
     ));
@@ -46,11 +47,13 @@ public function __construct() {
     // MockMenuBlockDeriver class ensures that only derivatives, and not the
     // base plugin, are available to the system.
     $this->discovery->setDefinition('menu', array(
+      'id' => 'menu',
       'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockMenuBlock',
       'deriver' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockMenuBlockDeriver',
     ));
     // A plugin defining itself as a derivative.
     $this->discovery->setDefinition('menu:foo', array(
+      'id' => 'menu',
       'label' => t('Base label'),
       'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockMenuBlock',
     ));
@@ -62,6 +65,7 @@ public function __construct() {
     // MockLayoutBlockDeriver class ensures that both the base plugin and the
     // derivatives are available to the system.
     $this->discovery->setDefinition('layout', array(
+      'id' => 'layout',
       'label' => t('Layout'),
       'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockLayoutBlock',
       'deriver' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockLayoutBlockDeriver',
@@ -70,6 +74,7 @@ public function __construct() {
     // A block plugin that requires context to function. This block requires a
     // user object in order to return the user name from the getTitle() method.
     $this->discovery->setDefinition('user_name', array(
+      'id' => 'user_name',
       'label' => t('User name'),
       'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockUserNameBlock',
       'context' => array(
@@ -79,6 +84,7 @@ public function __construct() {
 
     // An optional context version of the previous block plugin.
     $this->discovery->setDefinition('user_name_optional', array(
+      'id' => 'user_name_optional',
       'label' => t('User name optional'),
       'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockUserNameBlock',
       'context' => array(
@@ -88,12 +94,14 @@ public function __construct() {
 
     // A block plugin that requires a typed data string context to function.
     $this->discovery->setDefinition('string_context', array(
+      'id' => 'string_context',
       'label' => t('String typed data'),
       'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\TypedDataStringBlock',
     ));
 
     // A complex context plugin that requires both a user and node for context.
     $this->discovery->setDefinition('complex_context', array(
+      'id' => 'complex_context',
       'label' => t('Complex context'),
       'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockComplexContextBlock',
       'context' => array(
diff --git a/core/tests/Drupal/KernelTests/Core/Plugin/PluginTestBase.php b/core/tests/Drupal/KernelTests/Core/Plugin/PluginTestBase.php
index 3d651b1..dd5528b 100644
--- a/core/tests/Drupal/KernelTests/Core/Plugin/PluginTestBase.php
+++ b/core/tests/Drupal/KernelTests/Core/Plugin/PluginTestBase.php
@@ -58,31 +58,38 @@ protected function setUp() {
     );
     $this->mockBlockExpectedDefinitions = array(
       'user_login' => array(
+        'id' => 'user_login',
         'label' => 'User login',
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockUserLoginBlock',
       ),
       'menu:main_menu' => array(
+        'id' => 'menu',
         'label' => 'Main menu',
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockMenuBlock',
       ),
       'menu:navigation' => array(
+        'id' => 'menu',
         'label' => 'Navigation',
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockMenuBlock',
       ),
       'menu:foo' => array(
+        'id' => 'menu',
         'label' => 'Base label',
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockMenuBlock',
         'setting' => 'default',
       ),
       'layout' => array(
+        'id' => 'layout',
         'label' => 'Layout',
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockLayoutBlock',
       ),
       'layout:foo' => array(
+        'id' => 'layout',
         'label' => 'Layout Foo',
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockLayoutBlock',
       ),
       'user_name' => array(
+        'id' => 'user_name',
         'label' => 'User name',
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockUserNameBlock',
         'context' => array(
@@ -90,6 +97,7 @@ protected function setUp() {
         ),
       ),
       'user_name_optional' => array(
+        'id' => 'user_name_optional',
         'label' => 'User name optional',
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockUserNameBlock',
         'context' => array(
@@ -97,10 +105,12 @@ protected function setUp() {
         ),
       ),
       'string_context' => array(
+        'id' => 'string_context',
         'label' => 'String typed data',
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\TypedDataStringBlock',
       ),
       'complex_context' => array(
+        'id' => 'complex_context',
         'label' => 'Complex context',
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\mock_block\MockComplexContextBlock',
         'context' => array(
diff --git a/core/tests/Drupal/Tests/Core/Plugin/Discovery/DerivativeDiscoveryDecoratorTest.php b/core/tests/Drupal/Tests/Core/Plugin/Discovery/DerivativeDiscoveryDecoratorTest.php
index 07ba435..1e96458 100644
--- a/core/tests/Drupal/Tests/Core/Plugin/Discovery/DerivativeDiscoveryDecoratorTest.php
+++ b/core/tests/Drupal/Tests/Core/Plugin/Discovery/DerivativeDiscoveryDecoratorTest.php
@@ -94,6 +94,7 @@ public function testGetDerivativeFetcherWithAnnotationObjects() {
   public function testGetDeriverClassWithClassedDefinitions() {
     $definitions = array();
     $definition = $this->prophesize(DerivablePluginDefinitionInterface::class);
+    $definition->id()->willReturn('non_container_aware_discovery');
     $definition->getDeriver()->willReturn(TestDerivativeDiscoveryWithObject::class);
     $definitions['non_container_aware_discovery'] = $definition->reveal();