diff --git a/core/modules/auto_updates/auto_updates.install b/core/modules/auto_updates/auto_updates.install
index ff841b48a5..600babcf92 100644
--- a/core/modules/auto_updates/auto_updates.install
+++ b/core/modules/auto_updates/auto_updates.install
@@ -27,21 +27,21 @@ function auto_updates_requirements($phase) {
   $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']);
+    $requirements['auto_updates_readiness']['value'] = t('Your site has never checked if it is ready to apply <a href=":readiness_checks">automatic updates</a>.', [':readiness_checks' => 'https://www.drupal.org/docs/8/update/automatic-updates#readiness-checks']);
     if ($readiness_check->access()) {
-      $requirements['auto_updates_readiness']['description'] = t('<a href="@link">Run readiness checks</a> manually.', [
-        '@link' => $readiness_check->toString(),
+      $requirements['auto_updates_readiness']['description'] = t('<a href=":link">Run readiness checks</a> manually.', [
+        ':link' => $readiness_check->toString(),
       ]);
     }
   }
   elseif (!$checker_manager->hasRunRecently()) {
     $requirements['auto_updates_readiness']['severity'] = REQUIREMENT_ERROR;
     $time_ago = \Drupal::service('date.formatter')->formatTimeDiffSince($last_check_timestamp);
-    $requirements['auto_updates_readiness']['value'] = t('Your site has not recently 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']);
+    $requirements['auto_updates_readiness']['value'] = t('Your site has not recently checked if it is ready to apply <a href=":readiness_checks">automatic updates</a>.', [':readiness_checks' => 'https://www.drupal.org/docs/8/update/automatic-updates#readiness-checks']);
     if ($readiness_check->access()) {
-      $requirements['auto_updates_readiness']['description'] = t('Readiness checks were last run @time ago. <a href="@link">Run readiness checks</a> manually.', [
+      $requirements['auto_updates_readiness']['description'] = t('Readiness checks were last run @time ago. <a href=":link">Run readiness checks</a> manually.', [
         '@time' => $time_ago,
-        '@link' => $readiness_check->toString(),
+        ':link' => $readiness_check->toString(),
       ]);
     }
     else {
@@ -74,5 +74,7 @@ function auto_updates_requirements($phase) {
  * Implements hook_install().
  */
 function auto_updates_install($is_syncing) {
-  \Drupal::service('auto_updates.readiness_checker_manager')->run();
+  /** @var \Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface $checker_manager */
+  $checker_manager = \Drupal::service('auto_updates.readiness_checker_manager');
+  $checker_manager->run();
 }
diff --git a/core/modules/auto_updates/src/Form/SettingsForm.php b/core/modules/auto_updates/src/Form/SettingsForm.php
index 5899963879..96f634dfcb 100644
--- a/core/modules/auto_updates/src/Form/SettingsForm.php
+++ b/core/modules/auto_updates/src/Form/SettingsForm.php
@@ -57,15 +57,8 @@ public function getFormId() {
    */
   public function buildForm(array $form, FormStateInterface $form_state) {
     $config = $this->config('auto_updates.settings');
-
-    $form['readiness'] = [
-      '#type' => 'details',
-      '#title' => $this->t('Readiness checks'),
-      '#open' => TRUE,
-    ];
-
     $last_check_timestamp = $this->checkerManager->getTimestamp();
-    $form['readiness']['enable_readiness_checks'] = [
+    $form['enable_readiness_checks'] = [
       '#type' => 'checkbox',
       '#title' => $this->t('Check the readiness of automatically updating the site.'),
       '#default_value' => $config->get('enable_readiness_checks'),
@@ -74,7 +67,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       $readiness_messages = $last_check_timestamp === NULL ?
         $this->t('Readiness checks have never been run.')
         : $this->t('Readiness checks were last run @time ago.', ['@time' => $this->dateFormatter->formatTimeDiffSince($last_check_timestamp)]);
-      $form['readiness']['enable_readiness_checks']['#description'] = $readiness_messages . ' ' . $this->t('Manually <a href=":url">run the readiness checks</a>.', [
+      $form['enable_readiness_checks']['#description'] = $readiness_messages . ' ' . $this->t('Manually <a href=":url">run the readiness checks</a>.', [
         ':url' => Url::fromRoute('auto_updates.update_readiness')->toString(),
       ]);
     }
diff --git a/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php b/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
index e79d04f245..ea5a25c831 100644
--- a/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
@@ -5,7 +5,7 @@
 use Drupal\Component\FileSystem\FileSystem as FileSystemComponent;
 
 /**
- * The disk space readiness checker.
+ * A readiness checker that ensures there is enough disk space for updates.
  */
 class DiskSpace extends FileSystemBase {
 
@@ -26,16 +26,6 @@ class DiskSpace extends FileSystemBase {
    * {@inheritdoc}
    */
   protected function doCheck(): array {
-    return $this->diskSpaceCheck();
-  }
-
-  /**
-   * Check if the filesystem has sufficient disk space.
-   *
-   * @return \Drupal\Core\StringTranslation\TranslatableMarkup[]
-   *   An array of translatable strings if there is not sufficient space.
-   */
-  protected function diskSpaceCheck(): array {
     $messages = [];
     $minimum_megabytes = static::MINIMUM_DISK_SPACE / static::MEGABYTE_DIVISOR;
     if (!$this->areSameLogicalDisk($this->getRootPath(), $this->getVendorPath())) {
diff --git a/core/modules/auto_updates/src/ReadinessChecker/FileSystemBase.php b/core/modules/auto_updates/src/ReadinessChecker/FileSystemBase.php
index 3a25a35f0d..1a6fb8f1d5 100644
--- a/core/modules/auto_updates/src/ReadinessChecker/FileSystemBase.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/FileSystemBase.php
@@ -35,7 +35,7 @@ public function run(): array {
     if (!file_exists(implode(DIRECTORY_SEPARATOR, [$this->getRootPath(), 'core', 'core.api.php']))) {
       $messages[] = $this->t('The web root could not be located.');
     }
-    if (!is_dir($this->getVendorPath())) {
+    if (!file_exists(implode(DIRECTORY_SEPARATOR, [$this->getVendorPath(), 'autoload.php']))) {
       $messages[] = $this->t('Vendor folder "@vendor" is not a valid directory. Alternate vendor folder locations are not currently supported.', [
         '@vendor' => $this->getVendorPath(),
       ]);
diff --git a/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
index c7d17c23f5..f77076a6af 100644
--- a/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
@@ -7,7 +7,7 @@
 use Drupal\Core\KeyValueStore\KeyValueFactoryInterface;
 
 /**
- * Defines a chained readiness checker implementation combining multiple checks.
+ * Defines a manager to run readiness checkers.
  */
 class ReadinessCheckerManager implements ReadinessCheckerManagerInterface {
 
diff --git a/core/modules/auto_updates/tests/src/Functional/ReadinessCheckerTest.php b/core/modules/auto_updates/tests/src/Functional/ReadinessCheckerTest.php
index 248d7b0e81..44a0e09c6e 100644
--- a/core/modules/auto_updates/tests/src/Functional/ReadinessCheckerTest.php
+++ b/core/modules/auto_updates/tests/src/Functional/ReadinessCheckerTest.php
@@ -21,14 +21,14 @@ class ReadinessCheckerTest extends BrowserTestBase {
   /**
    * A user who can view the status report.
    *
-   * @var bool|\Drupal\user\Entity\User
+   * @var \Drupal\user\Entity\User
    */
   protected $reportViewerUser;
 
   /**
    * A user how can view the status report and run readiness checkers.
    *
-   * @var bool|\Drupal\user\Entity\User
+   * @var \Drupal\user\Entity\User
    */
   protected $checkerRunnerUser;
 
@@ -53,16 +53,20 @@ public function testReadinessChecksStatusReport() {
     $assert = $this->assertSession();
     $page = $this->getSession()->getPage();
 
+    // Disable automated_cron before installing auto_updates. This ensures we
+    // are testing that auto_updates runs the checkers when the module itself
+    // is installed and they weren't run on cron.
     $this->container->get('module_installer')->uninstall(['automated_cron']);
     $this->container->get('module_installer')->install(['auto_updates', 'auto_updates_test']);
 
     // 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);
-      $this->drupalGet('admin/reports/status');
-      $this->assertReadinessReportMatches('Your site is ready for automatic updates.');
-    }
+    $this->drupalLogin($this->reportViewerUser);
+    $this->drupalGet('admin/reports/status');
+    $this->assertReadinessReportMatches('Your site is ready for automatic updates.');
+    $this->drupalLogin($this->checkerRunnerUser);
+    $this->drupalGet('admin/reports/status');
+    $this->assertReadinessReportMatches('Your site is ready for automatic updates.');
 
     // Confirm a user without the permission to run readiness checks does not
     // have a link to run the checks when the checks need to be run again.
@@ -90,14 +94,15 @@ public function testReadinessChecksStatusReport() {
     $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) {
-      $this->drupalLogin($user);
-      // Confirm the error is displayed on the status report page.
-      $this->drupalGet('admin/reports/status');
-      $this->assertReadinessReportMatches('1 check failed: OMG 🚒. Your server is on 🔥!');
-      // @todo Should we always show when the checks were last run and a link to
-      //   run when there is an error?
-    }
+    // Confirm the error is displayed on the status report page.
+    $this->drupalGet('admin/reports/status');
+    $this->assertReadinessReportMatches('1 check failed: OMG 🚒. Your server is on 🔥!');
+    // @todo Should we always show when the checks were last run and a link to
+    //   run when there is an error?
+    // Confirm a user without permission to run the checks sees the same error.
+    $this->drupalLogin($this->reportViewerUser);
+    $this->drupalGet('admin/reports/status');
+    $this->assertReadinessReportMatches('1 check failed: OMG 🚒. Your server is on 🔥!');
 
     // Disable readiness checks.
     $this->drupalLogin($this->checkerRunnerUser);
@@ -109,7 +114,7 @@ public function testReadinessChecksStatusReport() {
     // last run is displayed.
     $assert->pageTextNotContains('Readiness checks have never been run.');
     $assert->pageTextNotContains('Readiness checks were last run');
-    $assert->pageTextNotContains('>run the readiness checks');
+    $assert->pageTextNotContains('run the readiness checks');
 
     // Confirm that access is denied when manually going to the readiness
     // checker controller.
@@ -153,7 +158,7 @@ public function testReadinessCheckAfterInstall() {
     // Confirm that installing a module that does not provide a new checker does
     // not run the checkers on install.
     $this->container->get('state')->set(TestChecker::STATE_KEY, 'Security has been compromised. "pass123" was a bad password!');
-    $this->container->get('module_installer')->install(['color']);
+    $this->container->get('module_installer')->install(['help']);
     $this->drupalGet('admin/reports/status');
     // Confirm that new checker message is not displayed because the checker was
     // not run again.