diff --git a/core/modules/system/src/Controller/SystemController.php b/core/modules/system/src/Controller/SystemController.php
index c848221dd2..578a8c743f 100644
--- a/core/modules/system/src/Controller/SystemController.php
+++ b/core/modules/system/src/Controller/SystemController.php
@@ -87,7 +87,7 @@ public function __construct(SystemManager $systemManager, ThemeAccessCheck $them
     $this->themeHandler = $theme_handler;
     $this->menuLinkTree = $menu_link_tree;
     if ($module_extension_list === NULL) {
-      @trigger_error('The extension.list.module service must be passed to ' . __NAMESPACE__ . '\SystemController::__construct. It was added in Drupal 8.9.0 and will be required before Drupal 9.0.0.', E_USER_DEPRECATED);
+      @trigger_error('The extension.list.module service must be passed to ' . __NAMESPACE__ . '\SystemController::__construct. It was added in Drupal 8.9.0 and will be required before Drupal 10.0.0.', E_USER_DEPRECATED);
       $module_extension_list = \Drupal::service('extension.list.module');
     }
     $this->moduleExtensionList = $module_extension_list;
diff --git a/core/modules/system/tests/src/Functional/Theme/ThemeUiTest.php b/core/modules/system/tests/src/Functional/Theme/ThemeUiTest.php
index 383acd46be..0414f3b63d 100644
--- a/core/modules/system/tests/src/Functional/Theme/ThemeUiTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/ThemeUiTest.php
@@ -59,27 +59,17 @@ public function testModulePermissions() {
    *
    * @dataProvider providerTestThemeInstallWithModuleDependencies
    */
-  public function testThemeInstallWithModuleDependencies(
-    $theme_name,
-    $first_expected_required_list_items,
-    $first_module_enable,
-    $first_confirm_checked,
-    $second_expected_required_list_items,
-    $second_module_enable,
-    $second_confirm_checked,
-    $disabled_attributes,
-    $required_by_messages,
-    $module_uninstall_message
-  ) {
+  public function testThemeInstallWithModuleDependencies($data) {
+    $theme_name = $data['theme_name'];
     $assert_session = $this->assertSession();
     $page = $this->getSession()->getPage();
     $this->drupalGet('admin/appearance');
 
-    $this->assertUninstallableTheme($first_expected_required_list_items, $theme_name);
+    $this->assertUninstallableTheme($data['first_expected_required_list_items'], $theme_name);
 
     // Enable one of the two required modules.
-    $this->drupalPostForm('admin/modules', $first_module_enable, 'Install');
-    foreach ($first_confirm_checked as $selector) {
+    $this->drupalPostForm('admin/modules', $data['first_module_enable'], 'Install');
+    foreach ($data['first_confirm_checked'] as $selector) {
       $this->assertSession()->elementExists('css', $selector);
     }
 
@@ -87,9 +77,9 @@ public function testThemeInstallWithModuleDependencies(
 
     // Confirm the theme is still uninstallable due to a remaining module
     // dependency.
-    $this->assertUninstallableTheme($second_expected_required_list_items, $theme_name);
-    $this->drupalPostForm('admin/modules', $second_module_enable, 'Install');
-    foreach ($second_confirm_checked as $selector) {
+    $this->assertUninstallableTheme($data['second_expected_required_list_items'], $theme_name);
+    $this->drupalPostForm('admin/modules', $data['second_module_enable'], 'Install');
+    foreach ($data['second_confirm_checked'] as $selector) {
       $this->assertSession()->elementExists('css', $selector);
     }
 
@@ -102,34 +92,67 @@ public function testThemeInstallWithModuleDependencies(
     // Confirm that the dependee modules can't be uninstalled because an enabled
     // theme depends on them.
     $this->drupalGet('admin/modules/uninstall');
-    foreach ($disabled_attributes as $attribute) {
+    foreach ($data['module_names'] as $attribute) {
       $assert_session->elementExists('css', "[name=\"uninstall[$attribute]\"][disabled]");
     }
-    foreach ($required_by_messages as $selector => $message) {
+    foreach ($data['required_by_messages'] as $selector => $message) {
       $assert_session->elementTextContains('css', $selector, $message);
     }
 
     // Uninstall the theme that depends on the modules, and confirm the modules
     // can now be uninstalled.
-    $this->drupalGet('admin/appearance');
-    $theme_to_uninstall = $theme_name === 'Test Theme with a Base Theme Depending on Modules' ? 'Test Theme Depending on Modules' : $theme_name;
-    $this->clickLink("Uninstall $theme_to_uninstall theme");
-    $assert_session->pageTextContains("The $theme_to_uninstall theme has been uninstalled.");
+    $this->uninstallTheme($theme_name);
     $this->drupalGet('admin/modules/uninstall');
 
-    foreach ($disabled_attributes as $attribute) {
+    // Only attempt to uninstall modules not required by the base theme.
+    $modules_to_uninstall = array_diff($data['module_names'], $data['base_theme_module_names']);
+    $this->uninstallModules($modules_to_uninstall, $data['module_uninstall_message']);
+
+    if (!empty($data['base_theme_to_uninstall'])) {
+      $base_theme_name = $data['base_theme_to_uninstall'];
+      $this->uninstallTheme($base_theme_name);
+      $this->drupalGet('admin/modules/uninstall');
+      $this->uninstallModules($data['base_theme_module_names'], $data['base_theme_module_uninstall_message']);
+    }
+  }
+
+  /**
+   * Uninstalls modules via the admin UI.
+   *
+   * @param string[] $module_names
+   *   An array of module machine names.
+   * @param string $confirmation_message_list
+   *   The list of modules included in the confirmation.
+   */
+  protected function uninstallModules(array $module_names, $confirmation_message_list) {
+    $assert_session = $this->assertSession();
+    $this->drupalGet('admin/modules/uninstall');
+    foreach ($module_names as $attribute) {
       $assert_session->elementExists('css', "[name=\"uninstall[$attribute]\"]:not([disabled])");
     }
     $to_uninstall = [];
-    foreach ($disabled_attributes as $attribute) {
+    foreach ($module_names as $attribute) {
       $to_uninstall["uninstall[$attribute]"] = 1;
     }
+    if (!empty($to_uninstall)) {
+      $this->drupalPostForm('admin/modules/uninstall', $to_uninstall, 'Uninstall');
+      $confirmation_message = 'The following modules will be completely uninstalled from your site, and all data from these modules will be lost!' . $confirmation_message_list . 'Would you like to continue with uninstalling the above?';
+      $assert_session->pageTextContains($confirmation_message);
+      $this->getSession()->getPage()->pressButton('Uninstall');
+      $assert_session->pageTextContains('The selected modules have been uninstalled.');
+    }
+  }
 
-    $this->drupalPostForm('admin/modules/uninstall', $to_uninstall, 'Uninstall');
-    $confirmation_message = 'The following modules will be completely uninstalled from your site, and all data from these modules will be lost!' . $module_uninstall_message . 'Would you like to continue with uninstalling the above?';
-    $assert_session->pageTextContains($confirmation_message);
-    $page->pressButton('Uninstall');
-    $assert_session->pageTextContains('The selected modules have been uninstalled.');
+  /**
+   * Uninstalls a theme via the admin UI.
+   *
+   * @param string $theme_name
+   *   The theme name.
+   */
+  protected function uninstallTheme($theme_name) {
+    $this->drupalGet('admin/appearance');
+    $this->clickLink("Uninstall $theme_name theme");
+    $this->assertSession()->pageTextContains("The $theme_name theme has been uninstalled.");
   }
 
   /**
@@ -138,139 +161,130 @@ public function testThemeInstallWithModuleDependencies(
   public function providerTestThemeInstallWithModuleDependencies() {
     return [
       'test theme with a module dependency and base theme with a different module dependency' => [
-        // $theme_name.
-        'Test Theme with a Module Dependency and Base Theme with a Different Module Dependency',
-        // $first_expected_required_list_items.
-        [
-          'Help (disabled)',
-          'Test Module Required by Theme (disabled)',
-          'Test Another Module Required by Theme (disabled)',
-        ],
-        // $first_module_enable.
-        [
-          'modules[test_module_required_by_theme][enable]' => 1,
-          'modules[test_another_module_required_by_theme][enable]' => 1,
-        ],
-        // $first_confirm_checked.
-        [
-          '#edit-modules-test-module-required-by-theme-enable[checked]',
-          '#edit-modules-test-another-module-required-by-theme-enable[checked]',
-        ],
-        // $second_expected_required_list_items.
-        [
-          'Help (disabled)',
-          'Test Module Required by Theme',
-          'Test Another Module Required by Theme',
-        ],
-        // $second_module_enable.
-        [
-          'modules[help][enable]' => 1,
-        ],
-        // $second_confirm_checked.
-        [
-          '#edit-modules-test-module-required-by-theme-enable[checked]',
-          '#edit-modules-test-another-module-required-by-theme-enable[checked]',
-          '#edit-modules-help-enable[checked]',
-        ],
-        // $disabled_attributes.
-        [
-          'help',
-        ],
-        // $required_by_messages.
         [
-          '[data-drupal-selector="edit-test-another-module-required-by-theme"] .item-list' => 'Required by the theme: test theme depending on modules',
-          '[data-drupal-selector="edit-test-module-required-by-theme"] .item-list' => 'Required by the theme: test theme depending on modules',
-          '[data-drupal-selector="edit-help"] .item-list' => 'Required by the theme: Test Theme with a Module Dependency and Base Theme with a Different Module Dependency',
-
+          'theme_name' => 'Test Theme with a Module Dependency and Base Theme with a Different Module Dependency',
+          'first_expected_required_list_items' => [
+            'Help (disabled)',
+            'Test Module Required by Theme (disabled)',
+            'Test Another Module Required by Theme (disabled)',
+          ],
+          'first_module_enable' => [
+            'modules[test_module_required_by_theme][enable]' => 1,
+            'modules[test_another_module_required_by_theme][enable]' => 1,
+          ],
+          'first_confirm_checked' => [
+            '#edit-modules-test-module-required-by-theme-enable[checked]',
+            '#edit-modules-test-another-module-required-by-theme-enable[checked]',
+          ],
+          'second_expected_required_list_items' => [
+            'Help (disabled)',
+            'Test Module Required by Theme',
+            'Test Another Module Required by Theme',
+          ],
+          'second_module_enable' => [
+            'modules[help][enable]' => 1,
+          ],
+          'second_confirm_checked' => [
+            '#edit-modules-test-module-required-by-theme-enable[checked]',
+            '#edit-modules-test-another-module-required-by-theme-enable[checked]',
+            '#edit-modules-help-enable[checked]',
+          ],
+          'module_names' => [
+            'help',
+            'test_module_required_by_theme',
+            'test_another_module_required_by_theme',
+          ],
+          'required_by_messages' => [
+            '[data-drupal-selector="edit-test-another-module-required-by-theme"] .item-list' => 'Required by the theme: Test Theme Depending on Modules',
+            '[data-drupal-selector="edit-test-module-required-by-theme"] .item-list' => 'Required by the theme: Test Theme Depending on Modules',
+            '[data-drupal-selector="edit-help"] .item-list' => 'Required by the theme: Test Theme with a Module Dependency and Base Theme with a Different Module Dependency',
+          ],
+          'module_uninstall_message' => 'help',
+          'base_theme_to_uninstall' => 'Test Theme Depending on Modules',
+          'base_theme_module_names' => [
+            'test_module_required_by_theme',
+            'test_another_module_required_by_theme',
+          ],
+          'base_theme_module_uninstall_message' => 'Test Another Module Required by ThemeTest Module Required by Theme',
         ],
-        // $module_uninstall_message.
-        'help',
       ],
-      'test theme depending on modules' => [
-        // $theme_name.
-        'Test Theme Depending on Modules',
-        // $first_expected_required_list_items.
-        [
-          'Test Module Required by Theme (disabled)',
-          'Test Another Module Required by Theme (disabled)',
-        ],
-        // $first_module_enable.
-        [
-          'modules[test_module_required_by_theme][enable]' => 1,
-        ],
-        // $first_confirm_checked.
-        [
-          '#edit-modules-test-module-required-by-theme-enable[checked]',
-        ],
-        // $second_expected_required_list_items.
-        [
-          'Test Module Required by Theme',
-          'Test Another Module Required by Theme (disabled)',
-        ],
-        // $second_module_enable.
-        [
-          'modules[test_another_module_required_by_theme][enable]' => 1,
-        ],
-        // $second_confirm_checked.
-        [
-          '#edit-modules-test-module-required-by-theme-enable[checked]',
-          '#edit-modules-test-another-module-required-by-theme-enable[checked]',
-        ],
-        // $disabled_attributes.
-        [
-          'test_module_required_by_theme',
-          'test_another_module_required_by_theme',
-        ],
-        // $required_by_messages.
+      'Test Theme Depending on Modules' => [
         [
-          '[data-drupal-selector="edit-test-another-module-required-by-theme"] .item-list' => 'Required by the theme: test theme depending on modules',
-          '[data-drupal-selector="edit-test-module-required-by-theme"] .item-list' => 'Required by the theme: test theme depending on modules',
+          'theme_name' => 'Test Theme Depending on Modules',
+          'first_expected_required_list_items' => [
+            'Test Module Required by Theme (disabled)',
+            'Test Another Module Required by Theme (disabled)',
+          ],
+          'first_module_enable' => [
+            'modules[test_module_required_by_theme][enable]' => 1,
+          ],
+          'first_confirm_checked' => [
+            '#edit-modules-test-module-required-by-theme-enable[checked]',
+          ],
+          'second_expected_required_list_items' => [
+            'Test Module Required by Theme',
+            'Test Another Module Required by Theme (disabled)',
+          ],
+          'second_module_enable' => [
+            'modules[test_another_module_required_by_theme][enable]' => 1,
+          ],
+          'second_confirm_checked' => [
+            '#edit-modules-test-module-required-by-theme-enable[checked]',
+            '#edit-modules-test-another-module-required-by-theme-enable[checked]',
+          ],
+          'module_names' => [
+            'test_module_required_by_theme',
+            'test_another_module_required_by_theme',
+          ],
+          'required_by_messages' => [
+            '[data-drupal-selector="edit-test-another-module-required-by-theme"] .item-list' => 'Required by the theme: Test Theme Depending on Modules',
+            '[data-drupal-selector="edit-test-module-required-by-theme"] .item-list' => 'Required by the theme: Test Theme Depending on Modules',
+          ],
+          'module_uninstall_message' => 'Test Another Module Required by ThemeTest Module Required by Theme',
+          'base_theme_to_uninstall' => '',
+          'base_theme_module_names' => [],
         ],
-        // $module_uninstall_message.
-        'test another module required by themetest module required by theme',
       ],
       'test theme with a base theme depending on modules' => [
-        // $theme_name.
-        'Test Theme with a Base Theme Depending on Modules',
-        // $first_expected_required_list_items.
-        [
-          'Test Module Required by Theme (disabled)',
-          'Test Another Module Required by Theme (disabled)',
-        ],
-        // $first_module_enable.
-        [
-          'modules[test_module_required_by_theme][enable]' => 1,
-        ],
-        // $first_confirm_checked.
-        [
-          '#edit-modules-test-module-required-by-theme-enable[checked]',
-        ],
-        // $second_expected_required_list_items.
-        [
-          'Test Module Required by Theme',
-          'Test Another Module Required by Theme (disabled)',
-        ],
-        // $second_module_enable.
-        [
-          'modules[test_another_module_required_by_theme][enable]' => 1,
-        ],
-        // $second_confirm_checked.
-        [
-          '#edit-modules-test-module-required-by-theme-enable[checked]',
-          '#edit-modules-test-another-module-required-by-theme-enable[checked]',
-        ],
-        // $disabled_attributes.
-        [
-          'test_module_required_by_theme',
-          'test_another_module_required_by_theme',
-        ],
-        // $required_by_messages.
         [
-          '[data-drupal-selector="edit-test-another-module-required-by-theme"] .item-list' => 'Required by the theme: test theme depending on modules',
-          '[data-drupal-selector="edit-test-module-required-by-theme"] .item-list' => 'Required by the theme: test theme depending on modules',
+          'theme_name' => 'Test Theme with a Base Theme Depending on Modules',
+          'first_expected_required_list_items' => [
+            'Test Module Required by Theme (disabled)',
+            'Test Another Module Required by Theme (disabled)',
+          ],
+          'first_module_enable' => [
+            'modules[test_module_required_by_theme][enable]' => 1,
+          ],
+          'first_confirm_checked' => [
+            '#edit-modules-test-module-required-by-theme-enable[checked]',
+          ],
+          'second_expected_required_list_items' => [
+            'Test Module Required by Theme',
+            'Test Another Module Required by Theme (disabled)',
+          ],
+          'second_module_enable' => [
+            'modules[test_another_module_required_by_theme][enable]' => 1,
+          ],
+          'second_confirm_checked' => [
+            '#edit-modules-test-module-required-by-theme-enable[checked]',
+            '#edit-modules-test-another-module-required-by-theme-enable[checked]',
+          ],
+          'module_names' => [
+            'test_module_required_by_theme',
+            'test_another_module_required_by_theme',
+          ],
+          'required_by_messages' => [
+            '[data-drupal-selector="edit-test-another-module-required-by-theme"] .item-list' => 'Required by the theme: Test Theme Depending on Modules',
+            '[data-drupal-selector="edit-test-module-required-by-theme"] .item-list' => 'Required by the theme: Test Theme Depending on Modules',
+          ],
+          'module_uninstall_message' => '',
+          'base_theme_to_uninstall' => 'Test Theme Depending on Modules',
+          'base_theme_module_names' => [
+            'test_module_required_by_theme',
+            'test_another_module_required_by_theme',
+          ],
+          'base_theme_module_uninstall_message' => 'Test Another Module Required by ThemeTest Module Required by Theme',
         ],
-        // $module_uninstall_message.
-        'test another module required by themetest module required by theme',
       ],
     ];
   }
diff --git a/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php b/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
index 30a7ba7841..df6f607d26 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
@@ -158,27 +158,27 @@ public function testInstallThemeWithUnmetModuleDependencies($theme_name, $missin
    */
   public function providerTestInstallThemeWithUnmetModuleDependencies() {
     return [
-      'test_theme_depending_on_modules' => [
+      'theme with uninstalled module dependencies' => [
         'test_theme_depending_on_modules',
         'test_module_required_by_theme, test_another_module_required_by_theme.',
         [],
       ],
-      'test_theme_with_a_base_theme_depending_on_modules' => [
+      'theme with a base theme with uninstalled module dependencies' => [
         'test_theme_with_a_base_theme_depending_on_modules',
         'test_module_required_by_theme, test_another_module_required_by_theme.',
         [],
       ],
-      'test_theme_mixed_module_dependencies' => [
+      'theme and base theme have uninstalled module dependencies' => [
         'test_theme_mixed_module_dependencies',
         'help, test_module_required_by_theme, test_another_module_required_by_theme.',
         [],
       ],
-      'test_theme_mixed_module_dependencies - node enabled' => [
+      'theme with already installed module dependencies, base theme module dependencies are not installed' => [
         'test_theme_mixed_module_dependencies',
         'test_module_required_by_theme, test_another_module_required_by_theme.',
         ['help'],
       ],
-      'test_theme_mixed_module_dependencies - test modules enabled' => [
+      'theme with module dependencies not installed, base theme module dependencies are already installed, ' => [
         'test_theme_mixed_module_dependencies',
         'help.',
         ['test_module_required_by_theme', 'test_another_module_required_by_theme'],