diff --git a/lib/tests/component_test.php b/lib/tests/component_test.php
index 917d2ad450b..0ee87636d99 100644
--- a/lib/tests/component_test.php
+++ b/lib/tests/component_test.php
@@ -17,6 +17,7 @@
 namespace core;
 
 use core\exception\coding_exception;
+use core\tests\fake_plugins_test_trait;
 use DirectoryIterator;
 use ReflectionClass;
 use ReflectionProperty;
@@ -32,6 +33,9 @@ use ReflectionProperty;
  * @covers \core\component
  */
 final class component_test extends \advanced_testcase {
+
+    use fake_plugins_test_trait;
+
     #[\Override]
     public function tearDown(): void {
         parent::tearDown();
@@ -1441,7 +1445,9 @@ final class component_test extends \advanced_testcase {
         $subplugins = $rcm->invoke(null, $pluginroot->url());
 
         $this->assertEquals([
-            'exampleplugina' => $pluginroot->getChild('apples')->url(),
+            'plugintypes' => [
+                'exampleplugina' => $pluginroot->getChild('apples')->url(),
+            ],
         ], $subplugins);
     }
 
@@ -1479,7 +1485,9 @@ final class component_test extends \advanced_testcase {
         $subplugins = $rcm->invoke(null, $pluginroot->url());
 
         $this->assertEquals([
-            'exampleplugina' => $pluginroot->getChild('apples')->url(),
+            'plugintypes' => [
+                'exampleplugina' => $pluginroot->getChild('apples')->url(),
+            ],
         ], $subplugins);
 
         $warnings = file_get_contents($logfile);
@@ -1624,4 +1632,342 @@ final class component_test extends \advanced_testcase {
             ],
         ];
     }
+
+    /**
+     * Test various methods when a deprecated plugin type is introduced.
+     *
+     * @runInSeparateProcess
+     * @return void
+     */
+    public function test_core_component_deprecated_plugintype(): void {
+        $this->resetAfterTest();
+
+        // Inject the 'fake' plugin type.
+        $this->add_full_mocked_plugintype(
+            plugintype: 'fake',
+            path: 'lib/tests/fixtures/fakeplugins/fake'
+        );
+
+        $componenthashbefore = component::get_all_component_hash();
+        $versionhashbefore = component::get_all_versions_hash();
+
+        // Deprecation-specific APIs - pre-deprecation.
+        $this->assertArrayHasKey('fake', component::get_plugin_types());
+        $this->assertArrayHasKey('fullfeatured', component::get_plugin_list('fake'));
+        $this->assertFalse(component::is_deprecated_plugin_type('fake'));
+        $this->assertFalse(component::is_deleted_plugin_type('fake'));
+        $this->assertFalse(component::is_plugintype_in_deprecation('fake'));
+        $this->assertArrayNotHasKey('fake', component::get_deprecated_plugin_types());
+        $this->assertArrayNotHasKey('fullfeatured', component::get_deprecated_plugin_list('fake'));
+        $this->assertArrayNotHasKey('fake', component::get_deleted_plugin_types());
+        $this->assertArrayNotHasKey('fullfeatured', component::get_deleted_plugin_list('fake'));
+        $this->assertArrayHasKey('fake', component::get_all_plugin_types());
+        $this->assertArrayHasKey('fullfeatured', component::get_all_plugins_list('fake'));
+
+        // Deprecate the fake plugintype via mocking component sources.
+        $this->deprecate_full_mocked_plugintype('fake');
+
+        // Verify before/after hashes have changed, since the plugintype is no longer part of the hash calcs.
+        $this->assertNotEquals(component::get_all_component_hash(), $componenthashbefore);
+        $this->assertNotEquals(component::get_all_versions_hash(), $versionhashbefore);
+
+        // Deprecation-specific APIs - post-deprecation.
+        $this->assertTrue(component::is_deprecated_plugin_type('fake'));
+        $this->assertFalse(component::is_deleted_plugin_type('fake'));
+        $this->assertTrue(component::is_plugintype_in_deprecation('fake'));
+        $this->assertArrayHasKey('fake', component::get_deprecated_plugin_types());
+        $this->assertArrayHasKey('fullfeatured', component::get_deprecated_plugin_list('fake'));
+        $this->assertArrayNotHasKey('fake', component::get_deleted_plugin_types());
+        $this->assertArrayNotHasKey('fullfeatured', component::get_deleted_plugin_list('fake'));
+        $this->assertArrayHasKey('fake', component::get_all_plugin_types());
+        $this->assertArrayHasKey('fullfeatured', component::get_all_plugins_list('fake'));
+
+        // Deprecated plugins excluded from the following for B/C.
+        $this->assertArrayNotHasKey('fake', component::get_plugin_types());
+        $this->assertArrayNotHasKey('fullfeatured', component::get_plugin_list('fake'));
+        $this->assertArrayNotHasKey('fake', component::get_component_list());
+        $this->assertEmpty(component::get_plugin_list_with_file('fake', 'classes/dummy.php'));
+        $this->assertEmpty(component::get_plugin_list_with_class('fake', 'dummy'));
+
+        // Deprecated plugins excluded by default for B/C, but can be included by request.
+        $this->assertNotContains('fake_fullfeatured', component::get_component_names());
+        $this->assertContains('fake_fullfeatured', component::get_component_names(false, true));
+
+        // Deprecated plugins included in the following.
+        $this->assertIsString(component::get_plugin_directory('fake', 'fullfeatured')); // Used by string manager.
+        $this->assertIsString(component::get_component_directory('fake_fullfeatured')); // Uses get_plugin_directory().
+        $this->assertTrue(component::has_monologo_icon('fake', 'fullfeatured'));  // Uses get_plugin_directory().
+        $this->assertEquals('fake_fullfeatured', component::get_component_from_classname(\fake_fullfeatured\example::class));
+
+        // Class autoloading of deprecated plugins is permitted, to facilitate plugin migration code.
+        $this->assertArrayHasKey('fake_fullfeatured\dummy',
+            component::get_component_classes_in_namespace('fake_fullfeatured'));
+        $this->assertTrue(class_exists(\fake_fullfeatured\dummy::class));
+    }
+
+    /**
+     * Test various core_component APIs when dealing with deleted plugin types.
+     *
+     * @runInSeparateProcess
+     * @return void
+     */
+    public function test_core_component_deleted_plugintype(): void {
+        $this->resetAfterTest();
+
+        // Inject the 'fake' plugin type.
+        $this->add_full_mocked_plugintype(
+            plugintype: 'fake',
+            path: 'lib/tests/fixtures/fakeplugins/fake',
+        );
+
+        // Delete the fake plugintype via mocking component sources.
+        $this->delete_full_mocked_plugintype('fake');
+
+        // Deprecation-specific methods.
+        $this->assertFalse(component::is_deprecated_plugin_type('fake'));
+        $this->assertTrue(component::is_deleted_plugin_type('fake'));
+        $this->assertTrue(component::is_plugintype_in_deprecation('fake'));
+        $this->assertArrayNotHasKey('fake', component::get_deprecated_plugin_types());
+        $this->assertArrayNotHasKey('fullfeatured', component::get_deprecated_plugin_list('fake'));
+        $this->assertArrayHasKey('fake', component::get_deleted_plugin_types());
+        $this->assertArrayHasKey('fullfeatured', component::get_deleted_plugin_list('fake'));
+        $this->assertArrayHasKey('fake', component::get_all_plugin_types());
+        $this->assertArrayHasKey('fullfeatured', component::get_all_plugins_list('fake'));
+
+        // Deleted plugintypes/plugins are not included in other methods.
+        $this->assertArrayNotHasKey('fake', component::get_plugin_types());
+        $this->assertArrayNotHasKey('fullfeatured', component::get_plugin_list('fake'));
+        $this->assertNotContains('fake_fullfeatured', component::get_component_names());
+        $this->assertNotContains('fake_fullfeatured', component::get_component_names(false, true));
+        $this->assertArrayNotHasKey('fake', component::get_component_list());
+        $this->assertEmpty(component::get_plugin_list_with_file('fake', 'classes/dummy.php'));
+        $this->assertEmpty(component::get_plugin_list_with_class('fake', 'dummy'));
+        $this->assertFalse(component::has_monologo_icon('fake', 'fullfeatured'));
+        $this->assertNull(component::get_plugin_directory('fake', 'fullfeatured'));
+        $this->assertNull(component::get_component_directory('fake_fullfeatured'));
+        $this->assertNull(component::get_component_from_classname(\fake_fullfeatured\example::class));
+
+        // Class autoloading of deleted plugins is not supported.
+        $this->assertArrayNotHasKey('fake_fullfeatured\dummy',
+            component::get_component_classes_in_namespace('fake_fullfeatured'));
+        $this->assertFalse(class_exists(fake_fullfeatured\dummy::class));
+    }
+
+    /**
+     * Test various core_component APIs when dealing with deprecated subplugins.
+     *
+     * @runInSeparateProcess
+     * @return void
+     */
+    public function test_core_component_deprecated_subplugintype(): void {
+        $this->resetAfterTest();
+
+        // Inject the 'fake' plugin type. This includes three mock subplugins:
+        // 1. fullsubtype_example: a regular plugin type, not deprecated, nor deleted.
+        // 2. fulldeprecatedsubtype_test: a deprecated subplugin type.
+        // 3. fulldeletedsubtype_demo: a deleted subplugin type.
+        $this->add_full_mocked_plugintype(
+            plugintype: 'fake',
+            path: 'lib/tests/fixtures/fakeplugins/fake',
+            subpluginsupport: true
+        );
+        $this->assert_deprecation_apis_subplugins();
+    }
+
+    /**
+     * Verify that a plugin which supports subplugins cannot be deprecated.
+     *
+     * @runInSeparateProcess
+     * @return void
+     */
+    public function test_core_component_deprecated_subplugintype_supporting_subplugins(): void {
+        $this->resetAfterTest();
+
+        // Inject the 'fake' plugin type. This includes three mock subplugins:
+        // 1. fullsubtype_example: a regular plugin type, not deprecated, nor deleted.
+        // 2. fulldeprecatedsubtype_test: a deprecated subplugin type.
+        // 3. fulldeletedsubtype_demo: a deleted subplugin type.
+        $this->add_full_mocked_plugintype(
+            plugintype: 'fake',
+            path: 'lib/tests/fixtures/fakeplugins/fake',
+            subpluginsupport: true
+        );
+
+        // Try to deprecate the fake plugintype via mocking component sources.
+        $this->deprecate_full_mocked_plugintype('fake');
+
+        // Deprecation unsupported, so verify core_component treats all plugins the same as before the deprecation attempt.
+        // Debugging is expected to be emitted during core_component::init().
+        $this->assert_deprecation_apis_subplugins();
+        $this->assertDebuggingCalled('Deprecation of a plugin type which supports subplugins is not supported. ' .
+            'These plugin types will continue to be treated as active.', DEBUG_DEVELOPER);
+    }
+
+    /**
+     * Verify that a plugin which supports subplugins cannot be deleted.
+     *
+     * @runInSeparateProcess
+     * @return void
+     */
+    public function test_core_component_deleted_subplugintype_supporting_subplugins(): void {
+        $this->resetAfterTest();
+
+        // Inject the 'fake' plugin type. This includes three mock subplugins:
+        // 1. fullsubtype_example: a regular plugin type, not deprecated, nor deleted.
+        // 2. fulldeprecatedsubtype_test: a deprecated subplugin type.
+        // 3. fulldeletedsubtype_demo: a deleted subplugin type.
+        $this->add_full_mocked_plugintype(
+            plugintype: 'fake',
+            path: 'lib/tests/fixtures/fakeplugins/fake',
+            subpluginsupport: true
+        );
+
+        // Try to delete the fake plugintype via mocking component sources.
+        $this->delete_full_mocked_plugintype('fake');
+
+        // Deletion unsupported, so verify core_component treats all plugins the same as before the deletion attempt.
+        // Debugging is expected to be emitted during core_component::init().
+        $this->assert_deprecation_apis_subplugins();
+        $this->assertDebuggingCalled('Deprecation of a plugin type which supports subplugins is not supported. ' .
+            'These plugin types will continue to be treated as active.', DEBUG_DEVELOPER);
+    }
+
+    /**
+     * Helper asserting the returns for various core_component APIs when dealing with deprecated and deleted subplugins.
+     *
+     * @return void
+     */
+    protected function assert_deprecation_apis_subplugins(): void {
+        // Deprecation-specific methods.
+        $this->assertFalse(component::is_deprecated_plugin_type('fake'));
+        $this->assertFalse(component::is_deprecated_plugin_type('fullsubtype'));
+        $this->assertTrue(component::is_deprecated_plugin_type('fulldeprecatedsubtype'));
+        $this->assertFalse(component::is_deprecated_plugin_type('fulldeletedsubtype'));
+
+        $this->assertFalse(component::is_deleted_plugin_type('fake'));
+        $this->assertFalse(component::is_deleted_plugin_type('fullsubtype'));
+        $this->assertFalse(component::is_deleted_plugin_type('fulldeprecatedsubtype'));
+        $this->assertTrue(component::is_deleted_plugin_type('fulldeletedsubtype'));
+
+        $this->assertFalse(component::is_plugintype_in_deprecation('fake'));
+        $this->assertFalse(component::is_plugintype_in_deprecation('fullsubtype'));
+        $this->assertTrue(component::is_plugintype_in_deprecation('fulldeprecatedsubtype'));
+        $this->assertTrue(component::is_plugintype_in_deprecation('fulldeletedsubtype'));
+
+        $this->assertArrayNotHasKey('fake', component::get_deprecated_plugin_types());
+        $this->assertArrayNotHasKey('fullsubtype', component::get_deprecated_plugin_types());
+        $this->assertArrayHasKey('fulldeprecatedsubtype', component::get_deprecated_plugin_types());
+        $this->assertArrayNotHasKey('fulldeletedsubtype', component::get_deprecated_plugin_types());
+
+        $this->assertArrayNotHasKey('fullfeatured', component::get_deprecated_plugin_list('fake'));
+        $this->assertArrayNotHasKey('example', component::get_deprecated_plugin_list('fullsubtype'));
+        $this->assertArrayHasKey('test', component::get_deprecated_plugin_list('fulldeprecatedsubtype'));
+        $this->assertArrayNotHasKey('demo', component::get_deprecated_plugin_list('fulldeletedsubtype'));
+
+        $this->assertArrayNotHasKey('fake', component::get_deleted_plugin_types());
+        $this->assertArrayNotHasKey('fullsubtype', component::get_deleted_plugin_types());
+        $this->assertArrayNotHasKey('fulldeprecatedsubtype', component::get_deleted_plugin_types());
+        $this->assertArrayHasKey('fulldeletedsubtype', component::get_deleted_plugin_types());
+
+        $this->assertArrayNotHasKey('fullfeatured', component::get_deleted_plugin_list('fake'));
+        $this->assertArrayNotHasKey('example', component::get_deleted_plugin_list('fullsubtype'));
+        $this->assertArrayNotHasKey('test', component::get_deleted_plugin_list('fulldeprecatedsubtype'));
+        $this->assertArrayHasKey('demo', component::get_deleted_plugin_list('fulldeletedsubtype'));
+
+        $this->assertArrayHasKey('fake', component::get_all_plugin_types());
+        $this->assertArrayHasKey('fullsubtype', component::get_all_plugin_types());
+        $this->assertArrayHasKey('fulldeprecatedsubtype', component::get_all_plugin_types());
+        $this->assertArrayHasKey('fulldeletedsubtype', component::get_all_plugin_types());
+
+        $this->assertArrayHasKey('fullfeatured', component::get_all_plugins_list('fake'));
+        $this->assertArrayHasKey('example', component::get_all_plugins_list('fullsubtype'));
+        $this->assertArrayHasKey('test', component::get_all_plugins_list('fulldeprecatedsubtype'));
+        $this->assertArrayHasKey('demo', component::get_all_plugins_list('fulldeletedsubtype'));
+
+        // Deprecated and deleted plugins excluded from the following for B/C.
+        $this->assertArrayHasKey('fake', component::get_plugin_types());
+        $this->assertArrayHasKey('fullsubtype', component::get_plugin_types());
+        $this->assertArrayNotHasKey('fulldeprecatedsubtype', component::get_plugin_types());
+        $this->assertArrayNotHasKey('fulldeletedsubtype', component::get_plugin_types());
+
+        $this->assertNotEmpty(component::get_plugin_list('fake'));
+        $this->assertNotEmpty(component::get_plugin_list('fullsubtype'));
+        $this->assertEmpty(component::get_plugin_list('fulldeprecatedsubtype'));
+        $this->assertEmpty(component::get_plugin_list('fulldeletedsubtype'));
+
+        $this->assertArrayHasKey('fake', component::get_component_list());
+        $this->assertArrayHasKey('fullsubtype', component::get_component_list());
+        $this->assertArrayNotHasKey('fulldeprecatedsubtype', component::get_component_list());
+        $this->assertArrayNotHasKey('fulldeletedsubtype', component::get_component_list());
+
+        $this->assertArrayHasKey('fullfeatured', component::get_plugin_list_with_file('fake', 'classes/dummy.php'));
+        $this->assertArrayHasKey('example', component::get_plugin_list_with_file('fullsubtype', 'classes/dummy.php'));
+        $this->assertEmpty(component::get_plugin_list_with_file('fulldeprecatedsubtype', 'classes/dummy.php'));
+        $this->assertEmpty(component::get_plugin_list_with_file('fulldeletedsubtype', 'classes/dummy.php'));
+
+        $this->assertArrayHasKey('fake_fullfeatured', component::get_plugin_list_with_class('fake', 'dummy'));
+        $this->assertArrayHasKey('fullsubtype_example', component::get_plugin_list_with_class('fullsubtype', 'dummy'));
+        $this->assertEmpty(component::get_plugin_list_with_class('fulldeprecatedsubtype', 'dummy'));
+        $this->assertEmpty(component::get_plugin_list_with_class('fulldeletedsubtype', 'dummy'));
+
+        $this->assertArrayHasKey('fullsubtype', component::get_subplugins('fake_fullfeatured'));
+        $this->assertContains('example', component::get_subplugins('fake_fullfeatured')['fullsubtype']);
+        $this->assertArrayNotHasKey('fulldeprecatedsubtype', component::get_subplugins('fake_fullfeatured'));
+        $this->assertArrayNotHasKey('fulldeletedsubtype', component::get_subplugins('fake_fullfeatured'));
+
+        $this->assertArrayHasKey('fullsubtype', component::get_all_subplugins('fake_fullfeatured'));
+        $this->assertContains('example', component::get_all_subplugins('fake_fullfeatured')['fullsubtype']);
+        $this->assertContains('test', component::get_all_subplugins('fake_fullfeatured')['fulldeprecatedsubtype']);
+        $this->assertContains('demo', component::get_all_subplugins('fake_fullfeatured')['fulldeletedsubtype']);
+
+        // Deprecated plugins excluded by default for B/C, but can be included by request.
+        // Deleted plugins are always excluded.
+        $this->assertContains('fake_fullfeatured', component::get_component_names());
+        $this->assertContains('fullsubtype_example', component::get_component_names());
+        $this->assertNotContains('fulldeprecatedsubtype_test', component::get_component_names());
+        $this->assertNotContains('fulldeletedsubtype_demo', component::get_component_names());
+        $this->assertContains('fulldeprecatedsubtype_test', component::get_component_names(false, true));
+        $this->assertNotContains('fulldeletedsubtype_demo', component::get_component_names(false, true));
+
+        // Deprecated plugins included in the following, but deleted plugins are excluded.
+        $this->assertIsString(component::get_plugin_directory('fake', 'fullfeatured')); // Used by string manager.
+        $this->assertIsString(component::get_plugin_directory('fullsubtype', 'example'));
+        $this->assertIsString(component::get_plugin_directory('fulldeprecatedsubtype', 'test'));
+        $this->assertNull(component::get_plugin_directory('fulldeletedsubtype', 'demo'));
+
+        $this->assertIsString(component::get_component_directory('fake_fullfeatured')); // Uses get_plugin_directory().
+        $this->assertIsString(component::get_component_directory('fullsubtype_example'));
+        $this->assertIsString(component::get_component_directory('fulldeprecatedsubtype_test'));
+        $this->assertNull(component::get_component_directory('fulldeletedsubtype_demo'));
+
+        $this->assertTrue(component::has_monologo_icon('fullsubtype', 'example')); // Uses get_plugin_directory().
+        $this->assertTrue(component::has_monologo_icon('fulldeprecatedsubtype', 'test'));
+        $this->assertFalse(component::has_monologo_icon('fulldeletedsubtype', 'demo'));
+
+        $this->assertEquals('fake_fullfeatured', component::get_component_from_classname(\fake_fullfeatured\example::class));
+        $this->assertEquals('fullsubtype_example',
+            component::get_component_from_classname(\fullsubtype_example\example::class));
+        $this->assertEquals('fulldeprecatedsubtype_test',
+            component::get_component_from_classname(\fulldeprecatedsubtype_test\example::class));
+        $this->assertNull(component::get_component_from_classname(\fulldeletedsubtype_demo\example::class));
+
+        // Deprecated and deleted plugins included in the following.
+        $this->assertEquals('fake_fullfeatured', component::get_subtype_parent('fullsubtype'));
+        $this->assertEquals('fake_fullfeatured', component::get_subtype_parent('fulldeprecatedsubtype'));
+        $this->assertEquals('fake_fullfeatured', component::get_subtype_parent('fulldeletedsubtype'));
+
+        // Class autoloading of deprecated plugins is permitted, to facilitate plugin migration code, but not for deleted plugins.
+        $this->assertArrayHasKey('fake_fullfeatured\dummy',
+            component::get_component_classes_in_namespace('fake_fullfeatured'));
+        $this->assertArrayHasKey('fullsubtype_example\dummy',
+            component::get_component_classes_in_namespace('fullsubtype_example'));
+        $this->assertArrayHasKey('fulldeprecatedsubtype_test\dummy',
+            component::get_component_classes_in_namespace('fulldeprecatedsubtype_test'));
+        $this->assertEquals([], component::get_component_classes_in_namespace('fulldeletedsubtype_demo'));
+
+        $this->assertTrue(class_exists(\fake_fullfeatured\dummy::class));
+        $this->assertTrue(class_exists(\fullsubtype_example\dummy::class));
+        $this->assertTrue(class_exists(\fulldeprecatedsubtype_test\dummy::class));
+        $this->assertFalse(class_exists(\fulldeletedsubtype_demo\dummy::class));
+    }
 }