diff -u b/core/modules/auto_updates/auto_updates.info.yml b/core/modules/auto_updates/auto_updates.info.yml
--- b/core/modules/auto_updates/auto_updates.info.yml
+++ b/core/modules/auto_updates/auto_updates.info.yml
@@ -1,6 +1,7 @@
 name: 'Automatic Updates'
 type: module
 description: 'Experimental module to develop automatic updates. Currently the module does not provide update functionality.'
+configure: auto_updates.settings
 package: Core (Experimental)
 version: VERSION
 hidden: true
diff -u b/core/modules/auto_updates/auto_updates.install b/core/modules/auto_updates/auto_updates.install
--- b/core/modules/auto_updates/auto_updates.install
+++ b/core/modules/auto_updates/auto_updates.install
@@ -5,9 +5,9 @@
  * Contains install and update functions for Automatic Updates.
  */
 
-use Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface;
 use Drupal\Core\StringTranslation\PluralTranslatableMarkup;
 use Drupal\Core\Url;
+use Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface;
 
 /**
  * Implements hook_requirements().
@@ -24,7 +24,7 @@
   }
   $requirements['auto_updates_readiness']['title'] = t('Update readiness checks');
   $readiness_check = Url::fromRoute('auto_updates.update_readiness');
-  $last_check_timestamp = $checker_manager->timestamp();
+  $last_check_timestamp = $checker_manager->getTimestamp();
   if ($last_check_timestamp === NULL) {
     $requirements['auto_updates_readiness']['severity'] = REQUIREMENT_ERROR;
     $requirements['auto_updates_readiness']['value'] = t('Your site has never checked if it is ready to apply <a href="@readiness_checks">automatic updates</a>.', ['@readiness_checks' => 'https://www.drupal.org/docs/8/update/automatic-updates#readiness-checks']);
@@ -76,5 +76,3 @@
 function auto_updates_install($is_syncing) {
-  /** @var \Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface $checker_manager */
-  $checker_manager = \Drupal::service('auto_updates.readiness_checker_manager');
-  $checker_manager->run();
+  \Drupal::service('auto_updates.readiness_checker_manager')->run();
 }
diff -u b/core/modules/auto_updates/auto_updates.module b/core/modules/auto_updates/auto_updates.module
--- b/core/modules/auto_updates/auto_updates.module
+++ b/core/modules/auto_updates/auto_updates.module
@@ -5,8 +5,8 @@
  * Provides hook implementations for Automatic Updates.
  */
 
-use Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface;
 use Drupal\Core\Url;
+use Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface;
 
 /**
  * Implements hook_page_top().
@@ -42,7 +42,7 @@
     }
     $results = $checker_manager->getResults(ReadinessCheckerManagerInterface::ERROR);
     if ($results) {
-      \Drupal::messenger()->addError(t('Your site is currently failing readiness checks for automatic updates. It cannot be <a href=":readiness_checks">automatically updated</a> until further action is performed:', [':readiness_checks' => 'https://www.drupal.org/docs/8/update/auto-updates#readiness-checks']));
+      \Drupal::messenger()->addError(t('Your site is currently failing readiness checks for automatic updates. It cannot be <a href=":readiness_checks">automatically updated</a> until further action is performed.', [':readiness_checks' => 'https://www.drupal.org/docs/8/update/auto-updates#readiness-checks']));
       foreach ($results as $message) {
         \Drupal::messenger()->addError($message);
       }
@@ -64,14 +64,11 @@
   $request_time = \Drupal::time()->getRequestTime();
   /** @var \Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface $checker_manager */
   $checker_manager = \Drupal::service('auto_updates.readiness_checker_manager');
-  $last_check = $checker_manager->timestamp();
+  $last_check = $checker_manager->getTimestamp();
   // Only allow cron to run once every hour.
   if ($last_check && ($request_time - $last_check) < 3600) {
     return;
   }
-
-  /** @var \Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface $checker_manager */
-  $checker_manager = \Drupal::service('auto_updates.readiness_checker_manager');
   $checker_manager->run();
 }
 
diff -u b/core/modules/auto_updates/auto_updates.routing.yml b/core/modules/auto_updates/auto_updates.routing.yml
--- b/core/modules/auto_updates/auto_updates.routing.yml
+++ b/core/modules/auto_updates/auto_updates.routing.yml
@@ -11,7 +11,7 @@
   path: '/admin/config/auto_updates/readiness'
   defaults:
     _controller: '\Drupal\auto_updates\Controller\ReadinessCheckerController::run'
-    _title: 'Update readiness checking...'
+    _title: 'Update readiness checking'
   requirements:
     _permission: 'administer software updates'
     _custom_access: '\Drupal\auto_updates\Controller\ReadinessCheckerController::access'
diff -u b/core/modules/auto_updates/src/Controller/ReadinessCheckerController.php b/core/modules/auto_updates/src/Controller/ReadinessCheckerController.php
--- b/core/modules/auto_updates/src/Controller/ReadinessCheckerController.php
+++ b/core/modules/auto_updates/src/Controller/ReadinessCheckerController.php
@@ -17,7 +17,7 @@
 class ReadinessCheckerController extends ControllerBase {
 
   /**
-   * The readiness checker.
+   * The readiness checker manager.
    *
    * @var \Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface
    */
diff -u b/core/modules/auto_updates/src/Form/SettingsForm.php b/core/modules/auto_updates/src/Form/SettingsForm.php
--- b/core/modules/auto_updates/src/Form/SettingsForm.php
+++ b/core/modules/auto_updates/src/Form/SettingsForm.php
@@ -64,7 +64,7 @@
       '#open' => TRUE,
     ];
 
-    $last_check_timestamp = $this->checkerManager->timestamp();
+    $last_check_timestamp = $this->checkerManager->getTimestamp();
     $form['readiness']['enable_readiness_checks'] = [
       '#type' => 'checkbox',
       '#title' => $this->t('Check the readiness of automatically updating the site.'),
diff -u b/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php b/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
--- b/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
@@ -7,7 +7,7 @@
 /**
  * The disk space readiness checker.
  */
-class DiskSpace extends FilesystemBase {
+class DiskSpace extends FileSystemBase {
 
   /**
    * Minimum disk space (in bytes) is 100mb.
@@ -25,7 +25,7 @@
   /**
    * {@inheritdoc}
    */
-  protected function doCheck() {
+  protected function doCheck(): array {
     return $this->diskSpaceCheck();
   }
 
@@ -35,7 +35,7 @@
    * @return \Drupal\Core\StringTranslation\TranslatableMarkup[]
    *   An array of translatable strings if there is not sufficient space.
    */
-  protected function diskSpaceCheck() {
+  protected function diskSpaceCheck(): array {
     $messages = [];
     $minimum_megabytes = static::MINIMUM_DISK_SPACE / static::MEGABYTE_DIVISOR;
     if (!$this->areSameLogicalDisk($this->getRootPath(), $this->getVendorPath())) {
reverted:
--- b/core/modules/auto_updates/src/ReadinessChecker/FilesystemBase.php
+++ /dev/null
@@ -1,96 +0,0 @@
-<?php
-
-namespace Drupal\auto_updates\ReadinessChecker;
-
-use Drupal\Core\StringTranslation\StringTranslationTrait;
-
-/**
- * Base class for filesystem checkers.
- */
-abstract class FilesystemBase implements ReadinessCheckerInterface {
-  use StringTranslationTrait;
-
-  /**
-   * The root file path.
-   *
-   * @var string
-   */
-  protected $rootPath;
-
-  /**
-   * Filesystem constructor.
-   *
-   * @param string $app_root
-   *   The app root.
-   */
-  public function __construct(string $app_root) {
-    $this->rootPath = $app_root;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function run() {
-    $messages = [];
-    if (!file_exists($this->getRootPath() . DIRECTORY_SEPARATOR . implode(DIRECTORY_SEPARATOR, ['core', 'core.api.php']))) {
-      $messages[] = $this->t('The web root could not be located.');
-    }
-    if (!is_dir($this->getVendorPath())) {
-      $messages[] = $this->t('Vendor folder "@vendor" is not a valid directory. Alternate vendor folder locations are not currently supported.', [
-        '@vendor' => $this->getVendorPath(),
-      ]);
-    }
-    if ($messages) {
-      return $messages;
-    }
-    return $this->doCheck();
-  }
-
-  /**
-   * Perform checks.
-   *
-   * @return array
-   *   An array of translatable strings if any checks fail.
-   */
-  abstract protected function doCheck();
-
-  /**
-   * Get the root file path.
-   *
-   * @return string
-   *   The root file path.
-   */
-  protected function getRootPath() {
-    return $this->rootPath;
-  }
-
-  /**
-   * Get the vendor file path.
-   *
-   * @return string
-   *   The vendor file path.
-   */
-  protected function getVendorPath() {
-    // @todo Support finding the 'vendor' directory dynamically in
-    // https://www.drupal.org/node/3166435.
-    return $this->getRootPath() . DIRECTORY_SEPARATOR . 'vendor';
-  }
-
-  /**
-   * Determine if the root and vendor file system are the same logical disk.
-   *
-   * @param string $root
-   *   Root file path.
-   * @param string $vendor
-   *   Vendor file path.
-   *
-   * @return bool
-   *   TRUE if same file system, FALSE otherwise.
-   */
-  protected function areSameLogicalDisk(string $root, string $vendor) {
-    $root_statistics = stat($root);
-    $vendor_statistics = stat($vendor);
-    return $root_statistics && $vendor_statistics && $root_statistics['dev'] === $vendor_statistics['dev'];
-  }
-
-}
diff -u b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerInterface.php b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerInterface.php
--- b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerInterface.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerInterface.php
@@ -9,10 +9,11 @@
 
   /**
-   * Run check.
+   * Runs a check.
    *
    * @return array
-   *   An array of translatable strings or an empty array.
+   *   An array of translatable strings if any checks fail, otherwise an empty
+   *   array.
    */
-  public function run();
+  public function run(): array;
 
 }
diff -u b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
--- b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
@@ -12,9 +12,11 @@
 class ReadinessCheckerManager implements ReadinessCheckerManagerInterface {
 
   /**
-   * Last checked ago warning (in seconds).
+   * Time (in seconds) since the last check after which we generate a warning.
+   *
+   * Defaults to 1 day.
    */
-  private const LAST_CHECKED_WARNING = 3600 * 24;
+  private const LAST_CHECKED_WARNING = 60 * 60 * 24;
 
   /**
    * The key/value storage.
@@ -66,7 +68,7 @@
   /**
    * {@inheritdoc}
    */
-  public function addChecker(ReadinessCheckerInterface $checker, string $category = 'warning', $priority = 0) {
+  public function addChecker(ReadinessCheckerInterface $checker, string $category = 'warning', $priority = 0): ReadinessCheckerManagerInterface {
     if (!in_array($category, $this->getCategories(), TRUE)) {
       throw new \InvalidArgumentException(sprintf('Readiness checker category "%s" is invalid. Use "%s" instead.', $category, implode('" or "', $this->getCategories())));
     }
@@ -77,7 +79,7 @@
   /**
    * {@inheritdoc}
    */
-  public function run() {
+  public function run(): array {
     if (!$this->isEnabled()) {
       return [];
     }
@@ -91,7 +93,7 @@
       }
     }
 
-    $this->keyValue->set("readiness_check_results",
+    $this->keyValue->set('readiness_check_results',
       [
         'messages' => $messages_by_category,
         'checkers' => $this->getCurrentCheckerIds(),
@@ -104,9 +106,9 @@
   /**
    * {@inheritdoc}
    */
-  public function getResults($category) {
+  public function getResults($category): array {
     if ($this->isEnabled()) {
-      $results = $this->keyValue->get("readiness_check_results", []);
+      $results = $this->keyValue->get('readiness_check_results', []);
       $all_messages = $results['messages'] ?? [];
       return $all_messages[$category] ?? [];
     }
@@ -116,7 +118,7 @@
   /**
    * {@inheritdoc}
    */
-  public function clearStaleResults() {
+  public function clearStaleResults(): bool {
     $results = $this->keyValue->get('readiness_check_results');
     if (isset($results['checkers']) && $this->getCurrentCheckerIds() !== $results['checkers']) {
       $this->keyValue->delete('readiness_check_results');
@@ -128,21 +130,21 @@
   /**
    * {@inheritdoc}
    */
-  public function timestamp() {
+  public function getTimestamp(): int {
     return $this->keyValue->get('readiness_check_timestamp');
   }
 
   /**
    * {@inheritdoc}
    */
-  public function isEnabled() {
+  public function isEnabled(): bool {
     return $this->configFactory->get('auto_updates.settings')->get('enable_readiness_checks');
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getCategories() {
+  public function getCategories(): array {
     return [self::ERROR, self::WARNING];
   }
 
@@ -152,9 +154,9 @@
    * @return \Drupal\auto_updates\ReadinessChecker\ReadinessCheckerInterface[][]
    *   A nested and sorted array of checker objects. The first level of the
    *   array is keyed by checker categories. The second level array is checker
-   *   objects in the category order by priority.
+   *   objects in the category ordered by priority.
    */
-  protected function getSortedCheckers() {
+  protected function getSortedCheckers(): array {
     $sorted = [];
     foreach ($this->checkers as $category => $priorities) {
       foreach ($priorities as $checkers) {
@@ -170,7 +172,7 @@
    * Gets the current checker service Ids.
    *
    * @return string
-   *   A concatenated list of checker service Ids.
+   *   A concatenated list of checker service Ids delimited by '::'.
    */
   protected function getCurrentCheckerIds(): string {
     $service_ids = [];
@@ -185,8 +187,8 @@
   /**
    * {@inheritdoc}
    */
-  public function hasRunRecently() {
-    return !($this->time->getRequestTime() > $this->timestamp() + self::LAST_CHECKED_WARNING);
+  public function hasRunRecently(): bool {
+    return $this->time->getRequestTime() <= $this->getTimestamp() + self::LAST_CHECKED_WARNING;
   }
 
 }
diff -u b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php
--- b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php
@@ -24,75 +24,76 @@
    *   The checker interface to be appended to the checker chain.
    * @param string $category
-   *   (optional) The category of check.
+   *   (optional) The category of check. Defaults to 'warning'
    * @param int $priority
-   *   (optional) The priority of the checker being added. If not provided the
-   *   default priority is 0. Readiness checkers with larger priorities will run
-   *   first within a category.
+   *   (optional) The priority of the checker being added. Defaults to 0.
+   *   Readiness checkers with larger priorities will run first within a
+   *   category.
    *
    * @return $this
    */
-  public function addChecker(ReadinessCheckerInterface $checker, string $category = 'warning', $priority = 0);
+  public function addChecker(ReadinessCheckerInterface $checker, string $category = 'warning', $priority = 0): ReadinessCheckerManagerInterface;
 
   /**
-   * Run readiness checks.
+   * Runs readiness checks.
    *
    * @return string[][]
-   *   A nested array readiness check messages. The top level array is keyed by
-   *   category and the next level array is is an array of translatable strings
+   *   A nested array of readiness check messages. The top level array is keyed
+   *   by category and the next level array is an array of translatable strings
    *   for the category.
    */
-  public function run();
+  public function run(): array;
 
   /**
-   * Get results of most recent run.
+   * Gets the results of the most recent run.
    *
    * @param string $category
    *   The category of check.
    *
    * @return array
-   *   An array of translatable strings.
+   *   An array of translatable messages if any checks fail, otherwise an empty
+   *   array.
    */
-  public function getResults($category);
+  public function getResults($category): array;
 
   /**
-   * Get timestamp of most recent run.
+   * Gets the timestamp of the most recent run.
    *
    * @return int|null
-   *   A unix timestamp of most recent completed run if one exists or NULL if no
-   *   run has been completed.
+   *   The timestamp of the most recently completed run, or NULL if no run has
+   *   been completed.
    */
-  public function timestamp();
+  public function getTimestamp();
 
   /**
-   * Determine if readiness checks is enabled.
+   * Determines if readiness checks are enabled.
    *
    * @return bool
    *   TRUE if enabled, otherwise FALSE.
    */
-  public function isEnabled();
+  public function isEnabled(): bool;
 
   /**
-   * Get the checker categories.
+   * Gets the checker categories.
    *
    * @return string[]
    *   The checkers categories.
    */
-  public function getCategories();
+  public function getCategories(): array;
 
   /**
    * Clears readiness checker results if the available checkers have changed.
    *
    * @return bool
-   *   Return TRUE if the results were cleared, otherwise returns FALSE.
+   *   TRUE if the results were cleared, otherwise FALSE.
    */
-  public function clearStaleResults();
+  public function clearStaleResults(): bool;
 
   /**
    * Determines whether the readiness checkers have been run recently.
    *
    * @return bool
-   *   True if the checkers have been run recently, otherwise false.
+   *   TRUE if the checkers have been run recently, otherwise FALSE.
    */
-  public function hasRunRecently();
+  public function hasRunRecently(): bool;
 
 }
reverted:
--- b/core/modules/auto_updates/tests/modules/auto_updates_test/auto_updates_test.info.yml
+++ a/core/modules/big_pipe/tests/modules/big_pipe_test/big_pipe_test.info.yml
@@ -1,5 +1,5 @@
+name: 'BigPipe test'
-name: 'Automatic Updates Test'
 type: module
+description: 'Support module for BigPipe testing.'
-description: 'Module for testing Automatic Updates.'
 package: Testing
 version: VERSION
reverted:
--- b/core/modules/auto_updates/tests/modules/auto_updates_test/src/Datetime/TestTime.php
+++ a/core/modules/update/tests/modules/update_test/src/Datetime/TestTime.php
@@ -1,6 +1,6 @@
 <?php
 
+namespace Drupal\update_test\Datetime;
-namespace Drupal\auto_updates_test\Datetime;
 
 use Drupal\Component\Datetime\Time;
 
@@ -9,16 +9,12 @@
  */
 class TestTime extends Time {
 
-  const TIME_FORMAT = 'U';
-
-  const STATE_KEY = 'auto_updates_test.mock_date_time';
-
   /**
    * {@inheritdoc}
    */
   public function getRequestTime() {
+    if ($mock_date = \Drupal::state()->get('update_test.mock_date', NULL)) {
+      return \DateTime::createFromFormat('Y-m-d', $mock_date)->getTimestamp();
-    if ($mock_date = \Drupal::state()->get(TestTime::STATE_KEY, NULL)) {
-      return \DateTime::createFromFormat(self::TIME_FORMAT, $mock_date)->getTimestamp();
     }
     return parent::getRequestTime();
   }
diff -u b/core/modules/auto_updates/tests/modules/auto_updates_test/src/ReadinessChecker/TestChecker.php b/core/modules/auto_updates/tests/modules/auto_updates_test/src/ReadinessChecker/TestChecker.php
--- b/core/modules/auto_updates/tests/modules/auto_updates_test/src/ReadinessChecker/TestChecker.php
+++ b/core/modules/auto_updates/tests/modules/auto_updates_test/src/ReadinessChecker/TestChecker.php
@@ -17,7 +17,7 @@
   /**
    * {@inheritDoc}
    */
-  public function run() {
+  public function run(): array {
     if ($message = \Drupal::state()->get(static::STATE_KEY, NULL)) {
       return [$message];
     }
diff -u b/core/modules/auto_updates/tests/src/Functional/ReadinessCheckerTest.php b/core/modules/auto_updates/tests/src/Functional/ReadinessCheckerTest.php
--- b/core/modules/auto_updates/tests/src/Functional/ReadinessCheckerTest.php
+++ b/core/modules/auto_updates/tests/src/Functional/ReadinessCheckerTest.php
@@ -56,7 +56,7 @@
     $this->container->get('module_installer')->uninstall(['automated_cron']);
     $this->container->get('module_installer')->install(['auto_updates', 'auto_updates_test']);
 
-    // If the the site is ready for updates the users will see the same output
+    // If the site is ready for updates, the users will see the same output
     // regardless of whether the user has permission to run updates.
     foreach ([$this->reportViewerUser, $this->checkerRunnerUser] as $user) {
       $this->drupalLogin($user);
@@ -82,11 +82,12 @@
     // Run the readiness checks.
     $this->clickLink('Run readiness checks');
     // @todo If coming from the status report page should you be redirected there?
-    //   This is how 'Run cron" works.
+    //   This is how 'Run cron' works.
+    $assert->statusCodeEquals(200);
     $assert->addressEquals('/admin/config/auto_updates');
     $assert->checkboxChecked('enable_readiness_checks');
-    $assert->pageTextNotContains("Access denied");
-    $assert->pageTextContains('Your site is currently failing readiness checks for automatic updates. It cannot be automatically updated until further action is performed:');
+    $assert->pageTextNotContains('Access denied');
+    $assert->pageTextContains('Your site is currently failing readiness checks for automatic updates. It cannot be automatically updated until further action is performed.');
     $assert->pageTextContains('OMG 🚒. Your server is on 🔥!');
 
     foreach ([$this->reportViewerUser, $this->checkerRunnerUser] as $user) {
@@ -113,6 +114,7 @@
     // Confirm that access is denied when manually going to the readiness
     // checker controller.
     $this->drupalGet('admin/config/auto_updates/readiness');
+    $assert->statusCodeEquals(403);
     $assert->pageTextContains('Access denied');
 
     $this->drupalGet('admin/reports/status');
diff -u b/core/modules/auto_updates/tests/src/Kernel/ReadinessChecker/DiskSpaceTest.php b/core/modules/auto_updates/tests/src/Kernel/ReadinessChecker/DiskSpaceTest.php
--- b/core/modules/auto_updates/tests/src/Kernel/ReadinessChecker/DiskSpaceTest.php
+++ b/core/modules/auto_updates/tests/src/Kernel/ReadinessChecker/DiskSpaceTest.php
@@ -54,7 +54,7 @@
 }
 
 /**
- * Test checker with the free disk space minimum set to an insanely high number.
+ * Test checker with the free disk space minimum set to a very high number.
  */
 class TestDiskSpace extends DiskSpace {
 
@@ -73,7 +73,7 @@
   /**
    * {@inheritdoc}
    */
-  protected function areSameLogicalDisk(string $root, string $vendor) {
+  protected function areSameLogicalDisk(string $root, string $vendor): bool {
     return FALSE;
   }
 
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/auto_updates/src/ReadinessChecker/FileSystemBase.php
@@ -0,0 +1,96 @@
+<?php
+
+namespace Drupal\auto_updates\ReadinessChecker;
+
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+
+/**
+ * Base class for file system checkers.
+ */
+abstract class FileSystemBase implements ReadinessCheckerInterface {
+  use StringTranslationTrait;
+
+  /**
+   * The root file path.
+   *
+   * @var string
+   */
+  protected $rootPath;
+
+  /**
+   * FileSystemBase constructor.
+   *
+   * @param string $app_root
+   *   The app root.
+   */
+  public function __construct(string $app_root) {
+    $this->rootPath = $app_root;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function run(): array {
+    $messages = [];
+    if (!file_exists(implode(DIRECTORY_SEPARATOR, [$this->getRootPath(), 'core', 'core.api.php']))) {
+      $messages[] = $this->t('The web root could not be located.');
+    }
+    if (!is_dir($this->getVendorPath())) {
+      $messages[] = $this->t('Vendor folder "@vendor" is not a valid directory. Alternate vendor folder locations are not currently supported.', [
+        '@vendor' => $this->getVendorPath(),
+      ]);
+    }
+    if ($messages) {
+      return $messages;
+    }
+    return $this->doCheck();
+  }
+
+  /**
+   * Performs checks.
+   *
+   * @return array
+   *   An array of translatable strings if any checks fail.
+   */
+  abstract protected function doCheck(): array;
+
+  /**
+   * Gets the root file path.
+   *
+   * @return string
+   *   The root file path.
+   */
+  protected function getRootPath(): string {
+    return $this->rootPath;
+  }
+
+  /**
+   * Get the vendor file path.
+   *
+   * @return string
+   *   The vendor file path.
+   */
+  protected function getVendorPath(): string {
+    // @todo Support finding the 'vendor' directory dynamically in
+    // https://www.drupal.org/node/3166435.
+    return $this->getRootPath() . DIRECTORY_SEPARATOR . 'vendor';
+  }
+
+  /**
+   * Determines if the root and vendor directories are on the same logical disk.
+   *
+   * @param string $root
+   *   Root file path.
+   * @param string $vendor
+   *   Vendor file path.
+   *
+   * @return bool
+   *   TRUE if they are on the same file system, FALSE otherwise.
+   */
+  protected function areSameLogicalDisk(string $root, string $vendor): bool {
+    $root_statistics = stat($root);
+    $vendor_statistics = stat($vendor);
+    return $root_statistics && $vendor_statistics && $root_statistics['dev'] === $vendor_statistics['dev'];
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/auto_updates/tests/modules/auto_updates_test/auto_updates_test.info.yml
@@ -0,0 +1,5 @@
+name: 'Automatic Updates Test'
+type: module
+description: 'Module for testing Automatic Updates.'
+package: Testing
+version: VERSION
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/auto_updates/tests/modules/auto_updates_test/src/Datetime/TestTime.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace Drupal\auto_updates_test\Datetime;
+
+use Drupal\Component\Datetime\Time;
+
+/**
+ * Test service for altering the request time.
+ */
+class TestTime extends Time {
+
+  const TIME_FORMAT = 'U';
+
+  const STATE_KEY = 'auto_updates_test.mock_date_time';
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getRequestTime() {
+    if ($mock_date = \Drupal::state()->get(TestTime::STATE_KEY, NULL)) {
+      return \DateTime::createFromFormat(self::TIME_FORMAT, $mock_date)->getTimestamp();
+    }
+    return parent::getRequestTime();
+  }
+
+}