automatic_updates_extensions/tests/fixtures/packages_installed_with_composer_validator/theme_not_installed.staged.installed.json

-{
-    "packages": [
-        {
-            "name": "drupal/core-recommended",
-            "version": "9.8.0",
-            "require": {
-                "drupal/core": "9.8.0"
-            }
-        },
-        {
-            "name": "drupal/core",
-            "version": "9.8.0"
-        },
-        {
-            "name": "drupal/my_module",
-            "version": "9.8.0",
-            "type": "drupal-module"
-        },
-        {
-            "name": "drupal/my_dev_module",
-            "version": "9.8.1",
-            "type": "drupal-module"
-        },
-        {
-          "name": "drupal/new_theme",
-          "version": "9.8.0",
-          "type": "drupal-theme"
-        }
-    ],
-    "dev": true,
-    "dev-package-names": [
-        "drupal/my_dev_module"
-    ]
-}

automatic_updates_extensions/tests/fixtures/release-history/alpha.1.1.0.xml

 <?xml version="1.0" encoding="utf-8"?>
+<!--
+This fixture is used by  \Drupal\Tests\automatic_updates_extensions\Build\ModuleUpdateTest.
+
+Contains metadata about the following (fake) releases of alpha module, all of which are secure, in order:
+- 1.1.0
+- 1.0.0
+-->
 <project xmlns:dc="http://purl.org/dc/elements/1.1/">
 <title>Alpha</title>
 <short_name>alpha</short_name>

automatic_updates_extensions/tests/fixtures/release-history/automatic_updates_extensions_test_theme.1.1.xml

+<?xml version="1.0" encoding="utf-8"?>
+<!--
+This fixture is used by \Drupal\Tests\automatic_updates_extensions\Functional\UpdaterFormTest.
+
+Contains metadata about the following (fake) releases of automatic_updates_extensions_test_theme, all of which are secure, in order:
+- 3.0.0
+- 8.x-2.1
+- 8.x-2.0
+-->
+<project xmlns:dc="http://purl.org/dc/elements/1.1/">
+  <title>Automatic Updates Extensions Test Theme</title>
+  <short_name>automatic_updates_extensions_test_theme</short_name>
+  <dc:creator>drupal</dc:creator>
+  <type>project_theme</type>
+  <supported_branches>8.x-2.,3.0.</supported_branches>
+  <project_status>published</project_status>
+  <link>http://example.com/project/automatic_updates_extensions_test_theme</link>
+  <terms>
+    <term>
+      <name>Projects</name>
+      <value>Themes</value>
+    </term>
+    <term>
+      <name>Maintenance status</name>
+      <value>Minimally maintained</value>
+    </term>
+    <term>
+      <name>Development status</name>
+      <value>Under active development</value>
+    </term>
+  </terms>
+  <releases>
+    <release>
+      <name>automatic_updates_extensions_test_theme 3.0.0</name>
+      <version>3.0.0</version>
+      <tag>3.0.0</tag>
+      <status>published</status>
+      <release_link>http://example.com/automatic_updates_extensions_test_theme-3-0-0-release</release_link>
+      <download_link>http://example.com/automatic_updates_extensions_test_theme-3.0.0.tar.gz</download_link>
+      <date>1597793786</date>
+      <files>
+        <file>
+          <url>http://example.com/automatic_updates_extensions_test_theme-3.0.0.tar.gz</url>
+          <archive_type>tar.gz</archive_type>
+          <md5>43956be126b27d718ecffd0b17244aa1</md5>
+          <size>196080</size>
+          <filedate>1597793786</filedate>
+        </file>
+        <file>
+          <url>http://example.com/automatic_updates_extensions_test_theme-3.0.0.zip</url>
+          <archive_type>zip</archive_type>
+          <md5>5d24ec88ac4755af6ccbe6ef5ff8b3c9</md5>
+          <size>200399</size>
+          <filedate>1597793786</filedate>
+        </file>
+      </files>
+      <security covered="1">Covered by Drupal's security advisory policy</security>
+      <core_compatibility>^8 || ^9</core_compatibility>
+    </release>
+    <release>
+      <name>automatic_updates_extensions_test_theme 8.x-2.1</name>
+      <version>8.x-2.1</version>
+      <tag>8.x-2.1</tag>
+      <status>published</status>
+      <release_link>http://example.com/automatic_updates_extensions_test_theme-8-x-2-1-release</release_link>
+      <download_link>http://example.com/automatic_updates_extensions_test_theme-8.x-2.1.tar.gz</download_link>
+      <date>1597793786</date>
+      <files>
+        <file>
+          <url>http://example.com/automatic_updates_extensions_test_theme-8.x-2.1.tar.gz</url>
+          <archive_type>tar.gz</archive_type>
+          <md5>43956be126b27d718ecffd0b17244aa1</md5>
+          <size>196080</size>
+          <filedate>1597793786</filedate>
+        </file>
+        <file>
+          <url>http://example.com/automatic_updates_extensions_test_theme-8.x-2.1.zip</url>
+          <archive_type>zip</archive_type>
+          <md5>5d24ec88ac4755af6ccbe6ef5ff8b3c9</md5>
+          <size>200399</size>
+          <filedate>1597793786</filedate>
+        </file>
+      </files>
+      <terms>
+        <term>
+          <name>Release type</name>
+          <value>Bug fixes</value>
+        </term>
+      </terms>
+      <security covered="1">Covered by Drupal's security advisory policy</security>
+      <core_compatibility>8.x</core_compatibility>
+    </release>
+    <release>
+      <name>automatic_updates_extensions_test_theme 8.x-2.0</name>
+      <version>8.x-2.0</version>
+      <tag>8.x-2.0</tag>
+      <status>published</status>
+      <release_link>http://example.com/automatic_updates_extensions_test_theme-8-x-2-0-release</release_link>
+      <download_link>http://example.com/automatic_updates_extensions_test_theme-8.x-2.0.tar.gz</download_link>
+      <date>1597793786</date>
+      <files>
+        <file>
+          <url>http://example.com/automatic_updates_extensions_test_theme-8.x-2.0.tar.gz</url>
+          <archive_type>tar.gz</archive_type>
+          <md5>43956be126b27d718ecffd0b17244aa1</md5>
+          <size>196080</size>
+          <filedate>1597793786</filedate>
+        </file>
+        <file>
+          <url>http://example.com/automatic_updates_extensions_test_theme-8.x-2.0.zip</url>
+          <archive_type>zip</archive_type>
+          <md5>5d24ec88ac4755af6ccbe6ef5ff8b3c9</md5>
+          <size>200399</size>
+          <filedate>1597793786</filedate>
+        </file>
+      </files>
+      <terms>
+        <term>
+          <name>Release type</name>
+          <value>Bug fixes</value>
+        </term>
+      </terms>
+      <security covered="1">Covered by Drupal's security advisory policy</security>
+      <core_compatibility>8.x</core_compatibility>
+    </release>
+  </releases>
+</project>

automatic_updates_extensions/tests/fixtures/release-history/new_module.1.1.0.xml

 <?xml version="1.0" encoding="utf-8"?>
+<!--
+This fixture is used by  \Drupal\Tests\automatic_updates_extensions\Build\ModuleUpdateTest.
+
+Contains metadata about the following (fake) releases of new_module, all of which are secure, in order:
+- 1.1.0
+- 1.0.0
+-->
 <project xmlns:dc="http://purl.org/dc/elements/1.1/">
 <title>New Module</title>
 <short_name>new_module</short_name>

automatic_updates_extensions/tests/fixtures/release-history/semver_test.1.1.xml

 <?xml version="1.0" encoding="utf-8"?>
+<!--
+This fixture is used by \Drupal\Tests\automatic_updates_extensions\Functional\UpdaterFormTest.
+
+Contains metadata about the following (fake) releases of semver_test module, all of which are secure, in order:
+- 8.2.0, which is in an unsupported branch
+- 8.1.1
+- 8.1.1-beta1
+- 8.1.1-alpha1
+- 8.1.0
+- 8.1.0-beta1
+- 8.1.0-alpha1
+- 8.0.1
+- 8.0.1-beta1
+- 8.0.1-alpha1
+- 8.0.0
+- 8.0.0-beta1
+- 8.0.0-alpha1
+-->
 <project xmlns:dc="http://purl.org/dc/elements/1.1/">
 <title>Semver Test</title>
 <short_name>semver_test</short_name>

automatic_updates_extensions/tests/modules/automatic_updates_extensions_test/automatic_updates_extensions_test.info.yml

-name: 'Automatic Updates Extensions Test'
-description: 'Automatic Updates Extensions Test module'
+name: 'Automatic Updates Extensions Tests'
+description: 'Provides functional tests for recommended versions'
 type: module
 package: Testing
 dependencies:

automatic_updates_extensions/tests/modules/automatic_updates_extensions_test/automatic_updates_extensions_test.module

+<?php
+
+/**
+ * @file
+ * Contains hook implementation for Automatic Updates Extensions Test.
+ */
+
+/**
+ * Implements hook_update_status_alter().
+ */
+function automatic_updates_extensions_test_update_status_alter(&$projects) {
+  if (\Drupal::state()->get('testUninstallableRelease') && !empty($projects['semver_test'])) {
+    $projects['semver_test']['recommended'] = $projects['semver_test']['existing_version'];
+  }
+}

automatic_updates_extensions/tests/modules/automatic_updates_extensions_test/src/AutomaticUpdatesExtensionsTestServiceProvider.php

-<?php
-
-namespace Drupal\automatic_updates_extensions_test;
-
-use Drupal\Core\DependencyInjection\ContainerBuilder;
-use Drupal\Core\DependencyInjection\ServiceModifierInterface;
-
-/**
- * Service provider to use test updater service.
- */
-class AutomaticUpdatesExtensionsTestServiceProvider implements ServiceModifierInterface {
-
-  /**
-   * {@inheritdoc}
-   */
-  public function alter(ContainerBuilder $container) {
-    if ($container->hasDefinition('automatic_updates_extensions.updater')) {
-      $container->getDefinition('automatic_updates_extensions.updater')
-        ->setClass(TestExtensionUpdater::class);
-
-    }
-  }
-
-}

automatic_updates_extensions/tests/modules/automatic_updates_extensions_test/src/TestExtensionUpdater.php

-<?php
-
-namespace Drupal\automatic_updates_extensions_test;
-
-use Drupal\automatic_updates_extensions\ExtensionUpdater;
-use Drupal\package_manager\ComposerUtility;
-
-/**
- * Extends the updater to point to a fixture directory for the active Composer.
- */
-class TestExtensionUpdater extends ExtensionUpdater {
-
-  /**
-   * {@inheritdoc}
-   */
-  public function getActiveComposer(): ComposerUtility {
-    if ($path = \Drupal::state()->get('automatic_updates_extensions_test.active_path')) {
-      return ComposerUtility::createForDirectory($path);
-    }
-    return parent::getActiveComposer();
-  }
-
-}

automatic_updates_extensions/tests/modules/automatic_updates_extensions_test_api/automatic_updates_extensions_test_api.info.yml

@@ -4,3 +4,4 @@ type: module
 package: Testing
 dependencies:
   - automatic_updates:automatic_updates_extensions
+  - automatic_updates:package_manager_test_api

automatic_updates_extensions/tests/modules/automatic_updates_extensions_test_api/automatic_updates_extensions_test_api.routing.yml

@@ -4,3 +4,9 @@ automatic_updates_extensions_test_api:
     _controller: 'Drupal\automatic_updates_extensions_test_api\ApiController::run'
   requirements:
     _access: 'TRUE'
+automatic_updates_extensions_test_api.finish:
+  path: '/automatic-updates-extensions-test-api/finish/{id}'
+  defaults:
+    _controller: 'Drupal\automatic_updates_extensions_test_api\ApiController::finish'
+  requirements:
+    _access: 'TRUE'

automatic_updates_extensions/tests/modules/automatic_updates_extensions_test_api/src/ApiController.php

 <?php
 
+declare(strict_types = 1);
+
 namespace Drupal\automatic_updates_extensions_test_api;
 
-use Drupal\automatic_updates_extensions\ExtensionUpdater;
-use Drupal\Core\Controller\ControllerBase;
+use Drupal\automatic_updates_extensions\ExtensionUpdateStage;
 use Drupal\package_manager\PathLocator;
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpFoundation\Request;
+use Drupal\package_manager_test_api\ApiController as PackageManagerApiController;
 
 /**
- * Provides API endpoints to interact with a staging area in functional tests.
+ * Provides API endpoint to interact with stage directory in functional tests.
  */
-class ApiController extends ControllerBase {
-
-
-  /**
-   * The extension updater.
-   *
-   * @var \Drupal\automatic_updates_extensions\ExtensionUpdater
-   */
-  private $extensionUpdater;
-
-  /**
-   * The path locator service.
-   *
-   * @var \Drupal\package_manager\PathLocator
-   */
-  private $pathLocator;
+class ApiController extends PackageManagerApiController {
 
   /**
-   * Constructs an ApiController object.
-   *
-   * @param \Drupal\automatic_updates_extensions\ExtensionUpdater $extensionUpdater
-   *   The updater.
-   * @param \Drupal\package_manager\PathLocator $path_locator
-   *   The path locator service.
+   * {@inheritdoc}
    */
-  public function __construct(ExtensionUpdater $extensionUpdater, PathLocator $path_locator) {
-    $this->extensionUpdater = $extensionUpdater;
-    $this->pathLocator = $path_locator;
-  }
+  protected $finishedRoute = 'automatic_updates_extensions_test_api.finish';
 
   /**
    * {@inheritdoc}
    */
   public static function create(ContainerInterface $container) {
     return new static(
-      $container->get('automatic_updates_extensions.updater'),
-      $container->get('package_manager.path_locator')
+      $container->get(ExtensionUpdateStage::class),
+      $container->get(PathLocator::class),
     );
   }
 
   /**
-   * Runs a complete stage life cycle.
-   *
-   * Creates a staging area, requires packages into it, applies changes to the
-   * active directory, and destroys the stage.
-   *
-   * @param \Symfony\Component\HttpFoundation\Request $request
-   *   The request. The runtime and dev dependencies are expected to be in
-   *   either the query string or request body, under the 'runtime' and 'dev'
-   *   keys, respectively. There may also be a 'files_to_return' key, which
-   *   contains an array of file paths, relative to the project root, whose
-   *   contents should be returned in the response.
-   *
-   * @return \Symfony\Component\HttpFoundation\JsonResponse
-   *   A JSON response containing an associative array of the contents of the
-   *   files listed in the 'files_to_return' request key. The array will be
-   *   keyed by path, relative to the project root.
+   * {@inheritdoc}
    */
-  public function run(Request $request): JsonResponse {
-    $this->extensionUpdater->begin($request->get('projects', []));
-    $this->extensionUpdater->stage();
-    $this->extensionUpdater->apply();
-    $this->extensionUpdater->postApply();
-    $this->extensionUpdater->destroy();
-
-    $dir = $this->pathLocator->getProjectRoot();
-    $file_contents = [];
-    foreach ($request->get('files_to_return', []) as $path) {
-      $file_contents[$path] = file_get_contents($dir . '/' . $path);
-    }
-    return new JsonResponse($file_contents);
+  protected function createAndApplyStage(Request $request): string {
+    $id = $this->stage->begin($request->get('projects', []));
+    $this->stage->stage();
+    $this->stage->apply();
+    return $id;
   }
 
 }

automatic_updates_extensions/tests/src/Build/ModuleUpdateTest.php

 <?php
 
+declare(strict_types = 1);
+
 namespace Drupal\Tests\automatic_updates_extensions\Build;
 
 use Drupal\Tests\automatic_updates\Build\UpdateTestBase;
@@ -7,11 +9,12 @@ use Drupal\Tests\automatic_updates_extensions\Traits\FormTestTrait;
 use Symfony\Component\Filesystem\Filesystem as SymfonyFilesystem;
 
 /**
- * Tests updating modules in a staging area.
+ * Tests updating modules in a stage directory.
  *
  * @group automatic_updates_extensions
+ * @internal
  */
-class ModuleUpdateTest extends UpdateTestBase {
+final class ModuleUpdateTest extends UpdateTestBase {
 
   use FormTestTrait;
 
@@ -21,7 +24,7 @@ class ModuleUpdateTest extends UpdateTestBase {
   protected function createTestProject(string $template): void {
     parent::createTestProject($template);
     $this->setReleaseMetadata([
-      'drupal' => __DIR__ . '/../../../../tests/fixtures/release-history/drupal.9.8.1-security.xml',
+      'drupal' => __DIR__ . '/../../../../package_manager/tests/fixtures/release-history/drupal.9.8.2.xml',
       'alpha'  => __DIR__ . '/../../fixtures/release-history/alpha.1.1.0.xml',
       'new_module' => __DIR__ . '/../../fixtures/release-history/new_module.1.1.0.xml',
     ]);
@@ -37,32 +40,35 @@ class ModuleUpdateTest extends UpdateTestBase {
 \$config['update_test.settings']['system_info'] = $system_info;
 END;
     $this->writeSettings($code);
-
-    $this->addRepository('alpha', __DIR__ . '/../../../../package_manager/tests/fixtures/alpha/1.0.0');
-    $this->runComposer('COMPOSER_MIRROR_PATH_REPOS=1 composer require drupal/alpha --update-with-all-dependencies', 'project');
+    $alpha_repo_path = $this->copyFixtureToTempDirectory(__DIR__ . '/../../../../package_manager/tests/fixtures/build_test_projects/alpha/1.0.0');
+    $this->addRepository('alpha', $alpha_repo_path);
+    $this->runComposer('composer require drupal/alpha --update-with-all-dependencies', 'project');
     $this->assertModuleVersion('alpha', '1.0.0');
     $fs = new SymfonyFilesystem();
-    $fs->mirror(__DIR__ . '/../../fixtures/new_module', $this->getWorkspaceDirectory() . '/project/web/modules');
+    $fs->mirror($this->copyFixtureToTempDirectory(__DIR__ . '/../../fixtures/new_module'), $this->getWorkspaceDirectory() . '/project/web/modules');
     $this->installModules([
       'automatic_updates_extensions_test_api',
       'alpha',
       'new_module',
     ]);
 
-    // Change both modules' upstream version.
-    $this->addRepository('alpha', __DIR__ . '/../../../../package_manager/tests/fixtures/alpha/1.1.0');
+    // Change the module's upstream version.
+    static::copyFixtureFilesTo(__DIR__ . '/../../../../package_manager/tests/fixtures/build_test_projects/alpha/1.1.0', $alpha_repo_path);
+
+    // Ensure that none of the above changes have caused any status check or
+    // other errors on the status report.
+    $this->checkForUpdates();
+    $this->assertStatusReportChecksSuccessful();
   }
 
   /**
-   * Tests updating a module in a staging area via the API.
+   * Tests updating a module in a stage directory via the API.
    */
   public function testApi(): void {
     $this->createTestProject('RecommendedProject');
     // Use the API endpoint to create a stage and update the 'new_module' module
     // to 1.1.0.
     // @see \Drupal\automatic_updates_extensions_test_api\ApiController::run()
-    // There will be error in updating as this module is not installed
-    // via composer @see \Drupal\Tests\automatic_updates_extensions\Kernel\Validator\PackagesInstalledWithComposerValidatorTest.
     $query = http_build_query([
       'projects' => [
         'new_module' => '1.1.0',
@@ -72,36 +78,33 @@ END;
     $mink = $this->getMink();
     $mink->assertSession()->statusCodeEquals(500);
     $page_text = $mink->getSession()->getPage()->getText();
-    $this->assertStringContainsString('Automatic Updates can only update projects that were installed via Composer. The following packages are not installed through composer:', $page_text);
+    $this->assertStringContainsString('The project new_module is not a Drupal project known to Composer and cannot be updated.', $page_text);
     $this->assertStringContainsString('new_module', $page_text);
     // Use the API endpoint to create a stage and update the 'alpha' module to
-    // 1.1.0. We ask the API to return the contents of the module's
-    // composer.json file, so we can assert that they were updated to the
-    // version we expect.
-    // @see \Drupal\automatic_updates_extensions_test_api\ApiController::run()
-    $query = http_build_query([
-      'projects' => [
-        'alpha' => '1.1.0',
-      ],
-      'files_to_return' => [
-        'web/modules/contrib/alpha/composer.json',
-      ],
-    ]);
-    $this->visit("/automatic-updates-extensions-test-api?$query");
-    $mink = $this->getMink();
-    $mink->assertSession()->statusCodeEquals(200);
-
-    $file_contents = $mink->getSession()->getPage()->getContent();
-    $file_contents = json_decode($file_contents, TRUE);
-
-    $module_composer_json = json_decode($file_contents['web/modules/contrib/alpha/composer.json']);
-    $this->assertSame('1.1.0', $module_composer_json->version);
+    // 1.1.0.
+    $this->makePackageManagerTestApiRequest(
+      '/automatic-updates-extensions-test-api',
+      [
+        'projects' => [
+          'alpha' => '1.1.0',
+        ],
+      ]
+    );
+
+    $updated_composer_json = $this->getWebRoot() . 'modules/contrib/alpha/composer.json';
+    // Assert the module was updated.
+    $this->assertFileEquals(
+      __DIR__ . '/../../../../package_manager/tests/fixtures/build_test_projects/alpha/1.1.0/composer.json',
+      $updated_composer_json,
+    );
+    $this->assertRequestedChangesWereLogged(['Update drupal/alpha from 1.0.0 to 1.1.0']);
+    $this->assertAppliedChangesWereLogged(['Updated drupal/alpha from 1.0.0 to 1.1.0']);
   }
 
   /**
-   * Tests updating a module in a staging area via the UI.
+   * Tests updating a module in a stage directory via the UI.
    */
-  public function testUi() {
+  public function testUi(): void {
     $this->createTestProject('RecommendedProject');
 
     $mink = $this->getMink();
@@ -118,14 +121,35 @@ END;
     // Confirm that a 'New Module' project does not appear on the form.
     $assert_session->pageTextContains('Other updates were found, but they must be performed manually.');
     $assert_session->fieldNotExists('projects[new_module]');
+    // Ensure test failures provide helpful debug output when failing readiness
+    // checks prevent updates.
+    // @see \Drupal\Tests\WebAssert::buildStatusMessageSelector()
+    if ($error_message = $session->getPage()->find('xpath', '//div[@data-drupal-messages]//div[@aria-label="Error message"]')) {
+      /** @var \Behat\Mink\Element\NodeElement $error_message */
+      $this->assertSame('', $error_message->getText());
+    }
     $page->checkField('projects[alpha]');
     $page->pressButton('Update');
     $this->waitForBatchJob();
     $assert_session->pageTextContains('Ready to update');
+    $page->checkField('backup');
     $page->pressButton('Continue');
     $this->waitForBatchJob();
     $assert_session->pageTextContains('Update complete!');
     $this->assertModuleVersion('alpha', '1.1.0');
+    $this->assertRequestedChangesWereLogged(['Update drupal/alpha from 1.0.0 to 1.1.0']);
+    $this->assertAppliedChangesWereLogged(['Updated drupal/alpha from 1.0.0 to 1.1.0']);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function copyCodebase(\Iterator $iterator = NULL, $working_dir = NULL): void {
+    parent::copyCodebase($iterator, $working_dir);
+
+    // Ensure that we will install Drupal 9.8.0 (a fake version that should
+    // never exist in real life) initially.
+    $this->setUpstreamCoreVersion('9.8.0');
   }
 
   /**
@@ -154,7 +178,7 @@ END;
    * @param string $version
    *   The expected version.
    */
-  private function assertModuleVersion(string $module_name, string $version) {
+  private function assertModuleVersion(string $module_name, string $version): void {
     $web_root = $this->getWebRoot();
     $composer_json = file_get_contents("$web_root/modules/contrib/$module_name/composer.json");
     $data = json_decode($composer_json, TRUE);

automatic_updates_extensions/tests/src/Functional/ComposerStagerOperationFailureTest.php

+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\automatic_updates_extensions\Functional;
+
+use Drupal\package_manager_bypass\LoggingBeginner;
+use Drupal\package_manager_bypass\LoggingCommitter;
+use Drupal\package_manager_bypass\NoOpStager;
+use PhpTuf\ComposerStager\API\Exception\InvalidArgumentException;
+use PhpTuf\ComposerStager\API\Exception\LogicException;
+
+/**
+ * @covers \Drupal\automatic_updates_extensions\Form\UpdaterForm
+ * @group automatic_updates_extensions
+ * @internal
+ */
+class ComposerStagerOperationFailureTest extends UpdaterFormTestBase {
+
+  /**
+   * Tests Composer operation failure is handled properly.
+   *
+   * @param string $exception_class
+   *   The exception class.
+   * @param string $service_class
+   *   The Composer Stager service which should throw an exception.
+   *
+   * @dataProvider providerComposerOperationFailure
+   */
+  public function testComposerOperationFailure(string $exception_class, string $service_class): void {
+    $page = $this->getSession()->getPage();
+    $assert_session = $this->assertSession();
+    $this->setReleaseMetadata(__DIR__ . '/../../../../package_manager/tests/fixtures/release-history/drupal.9.8.2.xml');
+    $this->setReleaseMetadata(__DIR__ . '/../../fixtures/release-history/semver_test.1.1.xml');
+    $this->setProjectInstalledVersion(['semver_test' => '8.1.0']);
+    $this->checkForUpdates();
+    // Navigate to the update form.
+    $this->drupalGet('/admin/reports/updates');
+    $this->clickLink('Update Extensions');
+    $this->assertTableShowsUpdates(
+      'Semver Test',
+      '8.1.0',
+      '8.1.1',
+    );
+    $this->getStageFixtureManipulator()->setVersion('drupal/semver_test_package_name', '8.1.1');
+    $this->assertUpdatesCount(1);
+    $page->checkField('projects[semver_test]');
+
+    // Make the specified Composer Stager operation class throw an exception.
+    $message = $this->createComposeStagerMessage("Failure from inside $service_class");
+    $exception = new $exception_class($message);
+    call_user_func([$service_class, 'setException'], $exception);
+
+    // Start the update.
+    $page->pressButton('Update');
+    $this->checkForMetaRefresh();
+    // We can't continue the update after an error in the committer.
+    if ($service_class === LoggingCommitter::class) {
+      $this->acceptWarningAndUpdate();
+      $this->clickLink('the error page');
+      $assert_session->statusCodeEquals(200);
+      $assert_session->statusMessageContains('Automatic updates failed to apply, and the site is in an indeterminate state. Consider restoring the code and database from a backup.');
+      return;
+    }
+    $this->clickLink('the error page');
+    $assert_session->statusMessageContains($exception->getMessage());
+
+    // Make the same Composer Stager operation class NOT throw an exception.
+    call_user_func([$service_class, 'setException'], NULL);
+
+    // Stage should be automatically deleted when an error occurs.
+    $assert_session->buttonNotExists('Delete existing update');
+    // This ensures that we can still update after the exception no longer
+    // exists.
+    $page->checkField('projects[semver_test]');
+    $this->getStageFixtureManipulator()->setVersion('drupal/semver_test_package_name', '8.1.1');
+    $page->pressButton('Update');
+    $this->checkForMetaRefresh();
+    $this->acceptWarningAndUpdate();
+    $assert_session->statusMessageContains('Update complete!');
+  }
+
+  /**
+   * Data provider for testComposerOperationFailure().
+   *
+   * @return string[][]
+   *   The test cases.
+   */
+  public function providerComposerOperationFailure(): array {
+    return [
+      'LogicException from Beginner' => [LogicException::class, LoggingBeginner::class],
+      'LogicException from Stager' => [LogicException::class, NoOpStager::class],
+      'InvalidArgumentException from Stager' => [InvalidArgumentException::class, NoOpStager::class],
+      'LogicException from Committer' => [LogicException::class, LoggingCommitter::class],
+    ];
+  }
+
+}

automatic_updates_extensions/tests/src/Functional/DisplayUpdatesTest.php

+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\Tests\automatic_updates_extensions\Functional;
+
+/**
+ * @covers \Drupal\automatic_updates_extensions\Form\UpdaterForm
+ * @group automatic_updates_extensions
+ * @internal
+ */
+final class DisplayUpdatesTest extends UpdaterFormTestBase {
+
+  /**
+   * Data provider for testDisplayUpdates().
+   *
+   * @return array[]
+   *   The test cases.
+   */
+  public function providerDisplayUpdates(): array {
+    return [
+      'with unrequested updates' => [TRUE],
+      'without unrequested updates' => [FALSE],
+    ];
+  }
+
+  /**
+   * Tests the form displays the correct projects which will be updated.
+   *
+   * @param bool $unrequested_updates
+   *   Whether unrequested updates are present during update.
+   *
+   * @dataProvider providerDisplayUpdates
+   */
+  public function testDisplayUpdates(bool $unrequested_updates): void {
+    $this->container->get('theme_installer')->install(['automatic_updates_theme_with_updates']);
+    $this->setReleaseMetadata(__DIR__ . '/../../../../package_manager/tests/fixtures/release-history/drupal.9.8.2.xml');
+    $this->setReleaseMetadata(__DIR__ . "/../../fixtures/release-history/semver_test.1.1.xml");
+    $this->setReleaseMetadata(__DIR__ . "/../../../../package_manager/tests/fixtures/release-history/aaa_update_test.1.1.xml");
+    $this->setProjectInstalledVersion([
+      'semver_test' => '8.1.0',
+      'aaa_update_test' => '8.x-2.0',
+    ]);
+    $this->checkForUpdates();
+    $state = $this->container->get('state');
+    $page = $this->getSession()->getPage();
+
+    // Navigate to the automatic updates form.
+    $this->drupalGet('/admin/reports/updates');
+    $this->clickLink('Update Extensions');
+    $this->assertTableShowsUpdates(
+      'AAA Update test',
+      '8.x-2.0',
+      '8.x-2.1',
+    );
+    $this->assertTableShowsUpdates(
+      'Semver Test',
+      '8.1.0',
+      '8.1.1',
+      2
+    );
+    // User will choose both the projects to update and there will be no
+    // unrequested updates.
+    if ($unrequested_updates === FALSE) {
+      $page->checkField('projects[aaa_update_test]');
+    }
+    $page->checkField('projects[semver_test]');
+    $this->getStageFixtureManipulator()
+      ->setVersion('drupal/aaa_update_test', '2.1.0')
+      ->setVersion('drupal/semver_test_package_name', '8.1.1');
+    $page->pressButton('Update');
+    $this->checkForMetaRefresh();
+    $this->assertUpdateStagedTimes(1);
+    $assert_session = $this->assertSession();
+    // Both projects will be shown as requested updates if there are no
+    // unrequested updates, otherwise one project which user chose will be shown
+    // as requested update and other one will be shown as unrequested update.
+    if ($unrequested_updates === FALSE) {
+      $assert_session->pageTextNotContains('The following dependencies will also be updated:');
+    }
+    else {
+      $assert_session->pageTextContains('The following dependencies will also be updated:');
+    }
+    $assert_session->pageTextContains('The following projects will be updated:');
+    $assert_session->pageTextContains('Semver Test from 8.1.0 to 8.1.1');
+    $assert_session->pageTextContains('AAA Update test from 2.0.0 to 2.1.0');
+  }
+
+}

automatic_updates_extensions/tests/src/Functional/PreUpdateTest.php

+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\automatic_updates_extensions\Functional;
+
+use Drupal\fixture_manipulator\ActiveFixtureManipulator;
+
+/**
+ * @covers \Drupal\automatic_updates_extensions\Form\UpdaterForm
+ * @group automatic_updates_extensions
+ * @internal
+ */
+final class PreUpdateTest extends UpdaterFormTestBase {
+
+  /**
+   * Tests the form when modules requiring an update not installed via composer.
+   */
+  public function testNonComposerProjects(): void {
+    $this->setReleaseMetadata(__DIR__ . '/../../../../package_manager/tests/fixtures/release-history/aaa_update_test.1.1.xml');
+    $this->setReleaseMetadata(__DIR__ . '/../../fixtures/release-history/semver_test.1.1.xml');
+    $this->config('update.settings')
+      ->set('fetch.url', $this->baseUrl . '/test-release-history')
+      ->save();
+    $this->setProjectInstalledVersion(
+      [
+        'aaa_update_test' => '8.x-2.0',
+        'semver_test' => '8.1.0',
+      ]
+    );
+    // One module not installed through composer.
+    (new ActiveFixtureManipulator())
+      ->removePackage('drupal/aaa_update_test')
+      ->commitChanges();
+    $assert = $this->assertSession();
+    $user = $this->createUser(
+      [
+        'administer site configuration',
+        'administer software updates',
+      ]
+    );
+    $this->drupalLogin($user);
+    $this->checkForUpdates();
+    $this->drupalGet('admin/reports/updates/automatic-update-extensions');
+    $assert->pageTextContains('Other updates were found, but they must be performed manually. See the list of available updates for more information.');
+    $this->assertTableShowsUpdates('Semver Test', '8.1.0', '8.1.1');
+    $this->assertUpdatesCount(1);
+
+    // Both of the modules not installed through composer.
+    (new ActiveFixtureManipulator())
+      ->removePackage('drupal/semver_test_package_name')
+      ->commitChanges();
+    $this->getSession()->reload();
+    $assert->pageTextContains('Updates were found, but they must be performed manually. See the list of available updates for more information.');
+    $this->assertNoUpdates();
+  }
+
+  /**
+   * Tests the form when a module requires an update.
+   */
+  public function testHasUpdate(): void {
+    $this->setReleaseMetadata(__DIR__ . '/../../fixtures/release-history/semver_test.1.1.xml');
+    $assert = $this->assertSession();
+    $user = $this->createUser(['administer site configuration']);
+    $this->drupalLogin($user);
+    $this->setProjectInstalledVersion(['semver_test' => '8.1.0']);
+    $this->drupalGet('admin/reports/updates/automatic-update-extensions');
+    $assert->pageTextContains('Access Denied');
+    $assert->pageTextNotContains('Automatic Updates Form');
+    $user = $this->createUser(['administer software updates', 'administer site configuration']);
+    $this->drupalLogin($user);
+    $this->checkForUpdates();
+    $this->assertTableShowsUpdates('Semver Test', '8.1.0', '8.1.1');
+    $this->assertUpdatesCount(1);
+    $assert->pageTextContains('Automatic Updates Form');
+    $assert->buttonExists('Update');
+  }
+
+  /**
+   * Tests the form when there are no available updates.
+   */
+  public function testNoUpdate(): void {
+    $this->setReleaseMetadata(__DIR__ . '/../../fixtures/release-history/semver_test.1.1.xml');
+    $user = $this->createUser([
+      'administer site configuration',
+      'administer software updates',
+    ]);
+    $this->drupalLogin($user);
+    $this->setProjectInstalledVersion(['semver_test' => '8.1.1']);
+    $this->checkForUpdates();
+    $this->drupalGet('admin/reports/updates/automatic-update-extensions');
+    $this->assertNoUpdates();
+  }
+
+}

automatic_updates_extensions/tests/src/Functional/StatusCheckerRunAfterUpdateTest.php

+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\Tests\automatic_updates_extensions\Functional;
+
+use Drupal\automatic_updates_test\EventSubscriber\TestSubscriber1;
+use Drupal\package_manager\Event\StatusCheckEvent;
+use Drupal\package_manager\ValidationResult;
+
+/**
+ * @covers \Drupal\automatic_updates_extensions\Form\UpdaterForm
+ * @group automatic_updates_extensions
+ * @internal
+ */
+final class StatusCheckerRunAfterUpdateTest extends UpdaterFormTestBase {
+
+  /**
+   * Data provider for testStatusCheckerRunAfterUpdate().
+   *
+   * @return bool[][]
+   *   The test cases.
+   */
+  public function providerStatusCheckerRunAfterUpdate(): array {
+    return [
+      'has database updates' => [TRUE],
+      'does not have database updates' => [FALSE],
+    ];
+  }
+
+  /**
+   * Tests status checks are run after an update.
+   *
+   * @param bool $has_database_updates
+   *   Whether the site has database updates or not.
+   *
+   * @dataProvider providerStatusCheckerRunAfterUpdate
+   */
+  public function testStatusCheckerRunAfterUpdate(bool $has_database_updates): void {
+    $this->setReleaseMetadata(__DIR__ . '/../../fixtures/release-history/semver_test.1.1.xml');
+    $this->setProjectInstalledVersion(['semver_test' => '8.1.0']);
+    $this->checkForUpdates();
+    $page = $this->getSession()->getPage();
+    // Navigate to the automatic updates form.
+    $this->drupalGet('/admin/modules/automatic-update-extensions');
+    $assert_session = $this->assertSession();
+    $assert_session->pageTextNotContains(static::$errorsExplanation);
+    $assert_session->pageTextNotContains(static::$warningsExplanation);
+
+    $this->assertTableShowsUpdates('Semver Test', '8.1.0', '8.1.1');
+    $this->getStageFixtureManipulator()->setVersion('drupal/semver_test_package_name', '8.1.1');
+    $this->assertUpdatesCount(1);
+    $page->checkField('projects[semver_test]');
+    $page->pressButton('Update');
+    $this->checkForMetaRefresh();
+    $this->assertUpdateStagedTimes(1);
+    // Set an error before completing the update. This error should be visible
+    // on admin pages after completing the update without having to explicitly
+    // run the status checks.
+    TestSubscriber1::setTestResult([ValidationResult::createError([t('Error before continue.')])], StatusCheckEvent::class);
+    if ($has_database_updates) {
+      // Simulate a staged database update in the automatic_updates_test module.
+      // We must do this after the update has started, because the pending
+      // updates validator will prevent an update from starting.
+      $this->container->get('state')->set('automatic_updates_test.new_update', TRUE);
+      $this->acceptWarningAndUpdate();
+      $assert_session->pageTextContainsOnce('An error has occurred.');
+      $assert_session->pageTextContainsOnce('Continue to the error page');
+      $page->clickLink('the error page');
+      $assert_session->pageTextContains('Some modules have database schema updates to install. You should run the database update script immediately.');
+      $assert_session->linkExists('database update script');
+      $assert_session->linkByHrefExists('/update.php');
+      $page->clickLink('database update script');
+      $this->assertSession()->addressEquals('/update.php');
+      $assert_session->pageTextNotContains('Possible database updates have been detected in the following extension');
+      $page->clickLink('Continue');
+      // @see automatic_updates_update_1191934()
+      $assert_session->pageTextContains('Dynamic automatic_updates_update_1191934');
+      $page->clickLink('Apply pending updates');
+      $this->checkForMetaRefresh();
+      $assert_session->pageTextContains('Updates were attempted.');
+    }
+    else {
+      $this->acceptWarningAndUpdate();
+      $assert_session->addressEquals('/admin/reports/updates');
+      $assert_session->pageTextContainsOnce('Update complete!');
+    }
+    // Status checks should display errors on admin page.
+    $this->drupalGet('/admin');
+    // Confirm that the status checks were run and the new error is displayed.
+    $assert_session->statusMessageContains('Error before continue.', 'error');
+    $assert_session->statusMessageContains('Your site does not pass some readiness checks for automatic updates. It cannot be automatically updated until further action is performed.', 'error');
+    $assert_session->pageTextNotContains('Your site has not recently run an update readiness check. Rerun readiness checks now.');
+  }
+
+}

automatic_updates_extensions/tests/src/Functional/SuccessfulUpdateTest.php

+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\automatic_updates_extensions\Functional;
+
+use Drupal\package_manager\Event\PreApplyEvent;
+use Drupal\package_manager\LegacyVersionUtility;
+use Drupal\package_manager_test_validation\StagedDatabaseUpdateValidator;
+
+/**
+ * @covers \Drupal\automatic_updates_extensions\Form\UpdaterForm
+ * @group automatic_updates_extensions
+ * @internal
+ */
+final class SuccessfulUpdateTest extends UpdaterFormTestBase {
+
+  /**
+   * Data provider for testSuccessfulUpdate().
+   *
+   * @return mixed[][]
+   *   The test cases.
+   */
+  public function providerSuccessfulUpdate(): array {
+    return [
+      'maintenance mode on, semver module' => [
+        TRUE, 'semver_test', 'drupal/semver_test_package_name', 'Semver Test', '8.1.0', '8.1.1',
+      ],
+      'maintenance mode off, legacy module' => [
+        FALSE, 'aaa_update_test', 'drupal/aaa_update_test', 'AAA Update test', '8.x-2.0', '8.x-2.1',
+      ],
+      'maintenance mode off, legacy theme' => [
+        FALSE, 'automatic_updates_extensions_test_theme', 'drupal/automatic_updates_extensions_test_theme', 'Automatic Updates Extensions Test Theme', '8.x-2.0', '8.x-2.1',
+      ],
+    ];
+  }
+
+  /**
+   * Tests an update that has no errors or special conditions.
+   *
+   * @param bool $maintenance_mode_on
+   *   Whether maintenance should be on at the beginning of the update.
+   * @param string $project_name
+   *   The project name.
+   * @param string $package_name
+   *   The package name.
+   * @param string $project_title
+   *   The project title.
+   * @param string $installed_version
+   *   The installed version.
+   * @param string $target_version
+   *   The target version.
+   *
+   * @dataProvider providerSuccessfulUpdate
+   */
+  public function testSuccessfulUpdate(bool $maintenance_mode_on, string $project_name, string $package_name, string $project_title, string $installed_version, string $target_version): void {
+    $this->container->get('theme_installer')->install(['automatic_updates_theme_with_updates']);
+    // By default, the Update module only checks for updates of installed
+    // modules and themes. The two modules we're testing here (semver_test and
+    // aaa_update_test) are already installed by static::$modules.
+    $this->container->get('theme_installer')->install(['automatic_updates_extensions_test_theme']);
+    $this->setReleaseMetadata(__DIR__ . '/../../../../package_manager/tests/fixtures/release-history/drupal.9.8.2.xml');
+    $path_to_fixtures_folder = $project_name === 'aaa_update_test' ? '/../../../../package_manager/tests' : '/../..';
+    $this->setReleaseMetadata(__DIR__ . $path_to_fixtures_folder . '/fixtures/release-history/' . $project_name . '.1.1.xml');
+    $this->setProjectInstalledVersion([$project_name => $installed_version]);
+    $this->getStageFixtureManipulator()->setVersion($package_name, LegacyVersionUtility::convertToSemanticVersion($target_version));
+    $this->checkForUpdates();
+    $state = $this->container->get('state');
+    $state->set('system.maintenance_mode', $maintenance_mode_on);
+    StagedDatabaseUpdateValidator::setExtensionsWithUpdates([
+      'system',
+      'automatic_updates_theme_with_updates',
+    ]);
+
+    $page = $this->getSession()->getPage();
+    // Navigate to the automatic updates form.
+    $this->drupalGet('/admin/reports/updates');
+    $this->clickLink('Update Extensions');
+    $this->assertTableShowsUpdates(
+      $project_title,
+      $installed_version,
+      $target_version
+    );
+    $assert_session = $this->assertSession();
+    $this->assertUpdatesCount(1);
+
+    // Submit without selecting a project.
+    $page->pressButton('Update');
+    $assert_session->pageTextContains('Select one or more projects.');
+
+    // Submit with a project selected.
+    $page->checkField('projects[' . $project_name . ']');
+    $page->pressButton('Update');
+    $this->checkForMetaRefresh();
+    $this->assertUpdateStagedTimes(1);
+    // Confirm that the site was put into maintenance mode if needed.
+    $this->assertSame($state->get('system.maintenance_mode'), $maintenance_mode_on);
+
+    $assert_session->pageTextNotContains('The following dependencies will also be updated:');
+    // Ensure that a list of pending database updates is visible, along with a
+    // short explanation, in the warning messages.
+    $warning_messages = $assert_session->elementExists('xpath', '//div[@data-drupal-messages]//div[@aria-label="Warning message"]');
+    $this->assertStringContainsString('Database updates have been detected in the following extensions.<ul><li>System</li><li>Automatic Updates Theme With Updates</li></ul>', $warning_messages->getHtml());
+
+    $this->acceptWarningAndUpdate();
+    $assert_session->addressEquals('/admin/reports/updates');
+    // Confirm that the site was in maintenance before the update was applied.
+    // @see \Drupal\package_manager_test_validation\EventSubscriber\TestSubscriber::handleEvent()
+    $this->assertTrue($state->get(PreApplyEvent::class . '.system.maintenance_mode'));
+    $assert_session->pageTextContainsOnce('Update complete!');
+    // Confirm the site was returned to the original maintenance mode state.
+    $this->assertSame($state->get('system.maintenance_mode'), $maintenance_mode_on);
+    // Confirm that the apply and post-apply operations happened in
+    // separate requests.
+    // @see \Drupal\automatic_updates_test\EventSubscriber\RequestTimeRecorder
+    $pre_apply_time = $state->get('Drupal\package_manager\Event\PreApplyEvent time');
+    $post_apply_time = $state->get('Drupal\package_manager\Event\PostApplyEvent time');
+    $this->assertNotEmpty($pre_apply_time);
+    $this->assertNotEmpty($post_apply_time);
+    $this->assertNotSame($pre_apply_time, $post_apply_time);
+  }
+
+}

automatic_updates_extensions/tests/src/Functional/UnsuccessfulUpdateTest.php

+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\Tests\automatic_updates_extensions\Functional;
+
+use Drupal\automatic_updates_test\EventSubscriber\TestSubscriber1;
+use Drupal\package_manager\Event\StatusCheckEvent;
+use Drupal\package_manager\ValidationResult;
+use Drupal\package_manager_test_validation\EventSubscriber\TestSubscriber;
+
+/**
+ * @covers \Drupal\automatic_updates_extensions\Form\UpdaterForm
+ * @group automatic_updates_extensions
+ * @internal
+ */
+final class UnsuccessfulUpdateTest extends UpdaterFormTestBase {
+
+  /**
+   * Test the form for warning messages.
+   */
+  public function testWarnings(): void {
+    $this->setReleaseMetadata(__DIR__ . '/../../fixtures/release-history/semver_test.1.1.xml');
+    $assert = $this->assertSession();
+    $this->setProjectInstalledVersion(['semver_test' => '8.1.0']);
+    $this->checkForUpdates();
+    $message = t("Warning! Updating this module may cause an error.");
+    $warning = ValidationResult::createWarning([$message]);
+    TestSubscriber1::setTestResult([$warning], StatusCheckEvent::class);
+    // Navigate to the automatic updates form.
+    $this->drupalGet('/admin/reports/updates');
+    $this->clickLink('Update Extensions');
+    $this->assertTableShowsUpdates('Semver Test', '8.1.0', '8.1.1');
+    $this->getStageFixtureManipulator()->setVersion('drupal/semver_test_package_name', '8.1.1');
+    $this->assertUpdatesCount(1);
+    $this->checkForMetaRefresh();
+    $assert->pageTextNotContains(static::$errorsExplanation);
+    $assert->elementExists('css', '#edit-projects-semver-test')->check();
+    $assert->checkboxChecked('edit-projects-semver-test');
+    // No explanation is given for warnings.
+    $assert->pageTextNotContains(static::$warningsExplanation);
+    $assert->buttonExists('Update');
+
+    // Add warnings from StatusCheckEvent.
+    $summary_status_check_event = t('Some summary');
+    $messages_status_check_event = [
+      t("The only thing we're allowed to do is to"),
+      t("believe that we won't regret the choice"),
+      t("we made."),
+    ];
+    $warning_status_check_event = ValidationResult::createWarning($messages_status_check_event, $summary_status_check_event);
+    TestSubscriber::setTestResult([$warning_status_check_event], StatusCheckEvent::class);
+    $this->getSession()->getPage()->pressButton('Update');
+    $this->checkForMetaRefresh();
+    $assert->buttonExists('Continue');
+    $assert->pageTextContains((string) $summary_status_check_event);
+    foreach ($messages_status_check_event as $message) {
+      $assert->pageTextContains((string) $message);
+    }
+  }
+
+  /**
+   * Tests the form when an uninstallable module requires an update.
+   */
+  public function testUninstallableRelease(): void {
+    $this->container->get('state')->set('testUninstallableRelease', TRUE);
+    $this->setReleaseMetadata(__DIR__ . '/../../fixtures/release-history/semver_test.1.1.xml');
+    $this->setProjectInstalledVersion(['semver_test' => '8.1.0']);
+    $user = $this->createUser(['administer software updates', 'administer site configuration']);
+    $this->drupalLogin($user);
+    $this->drupalGet('admin/reports/updates/automatic-update-extensions');
+    $this->checkForUpdates();
+    $this->assertNoUpdates();
+  }
+
+}

automatic_updates_extensions/tests/src/Functional/UpdateErrorTest.php

+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\Tests\automatic_updates_extensions\Functional;
+
+use Drupal\automatic_updates_test\EventSubscriber\TestSubscriber1;
+use Drupal\package_manager\Event\StatusCheckEvent;
+use Drupal\package_manager\ValidationResult;
+use Drupal\package_manager_bypass\LoggingCommitter;
+use Drupal\package_manager_test_validation\EventSubscriber\TestSubscriber;
+
+/**
+ * @covers \Drupal\automatic_updates_extensions\Form\UpdaterForm
+ * @group automatic_updates_extensions
+ * @internal
+ */
+final class UpdateErrorTest extends UpdaterFormTestBase {
+
+  /**
+   * Tests that an exception is thrown if a previous apply failed.
+   */
+  public function testMarkerFileFailure(): void {
+    $this->setReleaseMetadata(__DIR__ . '/../../fixtures/release-history/semver_test.1.1.xml');
+    $this->setProjectInstalledVersion(['semver_test' => '8.1.0']);
+    $this->checkForUpdates();
+    $page = $this->getSession()->getPage();
+    // Navigate to the automatic updates form.
+    $this->drupalGet('/admin/modules/automatic-update-extensions');
+    $assert_session = $this->assertSession();
+    $assert_session->pageTextNotContains(static::$errorsExplanation);
+    $assert_session->pageTextNotContains(static::$warningsExplanation);
+
+    $this->assertTableShowsUpdates('Semver Test', '8.1.0', '8.1.1');
+    $this->getStageFixtureManipulator()->setVersion('drupal/semver_test_package_name', '8.1.1');
+    $this->assertUpdatesCount(1);
+    $page->checkField('projects[semver_test]');
+    $page->pressButton('Update');
+    $this->checkForMetaRefresh();
+    $this->assertUpdateStagedTimes(1);
+    $assert_session->pageTextNotContains('The following dependencies will also be updated:');
+    LoggingCommitter::setException(new \Exception('failed at committer'));
+    $this->acceptWarningAndUpdate();
+    $failure_message = 'Automatic updates failed to apply, and the site is in an indeterminate state. Consider restoring the code and database from a backup.';
+    $assert_session->pageTextContainsOnce('An error has occurred.');
+    $assert_session->pageTextContains($failure_message);
+    $page->clickLink('the error page');
+
+    // We should be on the form (i.e., 200 response code), but unable to
+    // continue the update.
+    $assert_session->statusCodeEquals(200);
+    $assert_session->pageTextContains($failure_message);
+    $assert_session->buttonNotExists('Continue');
+    // The same thing should be true if we try to start from the beginning.
+    $this->drupalGet('/admin/modules/automatic-update-extensions');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->pageTextContains($failure_message);
+    $assert_session->buttonNotExists('Update');
+  }
+
+  /**
+   * Test the form for errors.
+   */
+  public function testErrors(): void {
+    $this->setReleaseMetadata(__DIR__ . '/../../fixtures/release-history/semver_test.1.1.xml');
+    $assert = $this->assertSession();
+    $user = $this->createUser([
+      'administer site configuration',
+      'administer software updates',
+    ]);
+    $this->drupalLogin($user);
+    $this->setProjectInstalledVersion(['semver_test' => '8.1.0']);
+    $this->checkForUpdates();
+    $this->drupalGet('admin/reports/updates/automatic-update-extensions');
+    $this->assertTableShowsUpdates('Semver Test', '8.1.0', '8.1.1');
+    $this->assertUpdatesCount(1);
+    $message = t("You've not experienced Shakespeare until you have read him in the original Klingon.");
+    $error = ValidationResult::createError([$message]);
+    TestSubscriber1::setTestResult([$error], StatusCheckEvent::class);
+    $this->getSession()->reload();
+    $assert->pageTextContains((string) $message);
+    $assert->pageTextContains(static::$errorsExplanation);
+    $assert->pageTextNotContains(static::$warningsExplanation);
+    $assert->buttonNotExists('Update');
+  }
+
+  /**
+   * Tests that messages from StatusCheckEvent are shown on the confirmation form.
+   */
+  public function testStatusErrorMessages(): void {
+    $this->setReleaseMetadata(__DIR__ . '/../../fixtures/release-history/semver_test.1.1.xml');
+    $assert = $this->assertSession();
+    $this->setProjectInstalledVersion(['semver_test' => '8.1.0']);
+    $this->checkForUpdates();
+    $this->drupalGet('admin/reports/updates/automatic-update-extensions');
+    $this->assertTableShowsUpdates('Semver Test', '8.1.0', '8.1.1');
+    $this->assertUpdatesCount(1);
+    $this->getSession()->reload();
+    $assert->elementExists('css', '#edit-projects-semver-test')->check();
+    $assert->checkboxChecked('edit-projects-semver-test');
+    $assert->buttonExists('Update');
+    $messages = [
+      t("The only thing we're allowed to do is to"),
+      t("believe that we won't regret the choice"),
+      t("we made."),
+    ];
+    $summary = t('Some summary');
+    $error = ValidationResult::createError($messages, $summary);
+    TestSubscriber::setTestResult([$error], StatusCheckEvent::class);
+    $this->getSession()->getPage()->pressButton('Update');
+    $this->checkForMetaRefresh();
+    $assert->pageTextContains(static::$errorsExplanation);
+    $assert->pageTextNotContains(static::$warningsExplanation);
+    $assert->pageTextContains((string) $summary);
+    foreach ($messages as $message) {
+      $assert->pageTextContains((string) $message);
+    }
+    $assert->buttonNotExists('Continue');
+  }
+
+}