diff --git a/core/modules/auto_updates/src/Controller/ReadinessCheckerController.php b/core/modules/auto_updates/src/Controller/ReadinessCheckerController.php
index c2bb521490..bd3aac3fb8 100644
--- a/core/modules/auto_updates/src/Controller/ReadinessCheckerController.php
+++ b/core/modules/auto_updates/src/Controller/ReadinessCheckerController.php
@@ -4,6 +4,7 @@
 
 use Drupal\auto_updates\ReadinessChecker\ReadinessCheckerManagerInterface;
 use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Access\AccessResultInterface;
 use Drupal\Core\Controller\ControllerBase;
 use Drupal\Core\StringTranslation\TranslationInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -67,7 +68,7 @@ public function run() {
    * @return \Drupal\Core\Access\AccessResultInterface
    *   The access result.
    */
-  public function access() {
+  public function access(): AccessResultInterface {
     return AccessResult::allowedIf($this->checkerManager->isEnabled());
   }
 
diff --git a/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php b/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
index b97695900e..2cc5684d4a 100644
--- a/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/DiskSpace.php
@@ -2,8 +2,6 @@
 
 namespace Drupal\auto_updates\ReadinessChecker;
 
-use Drupal\Component\FileSystem\FileSystem as FileSystemComponent;
-
 /**
  * A readiness checker that ensures there is enough disk space for updates.
  */
diff --git a/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
index f77076a6af..2d855d3190 100644
--- a/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManager.php
@@ -106,7 +106,7 @@ public function run(): array {
   /**
    * {@inheritdoc}
    */
-  public function getResults($category): array {
+  public function getResults(string $category): array {
     if ($this->isEnabled()) {
       $results = $this->keyValue->get('readiness_check_results', []);
       $all_messages = $results['messages'] ?? [];
diff --git a/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php
index 0280b6663e..51923de26e 100644
--- a/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php
+++ b/core/modules/auto_updates/src/ReadinessChecker/ReadinessCheckerManagerInterface.php
@@ -23,7 +23,7 @@ interface ReadinessCheckerManagerInterface {
    * @param \Drupal\auto_updates\ReadinessChecker\ReadinessCheckerInterface $checker
    *   The checker interface to be appended to the checker chain.
    * @param string $category
-   *   (optional) The category of check. Defaults to 'warning'
+   *   (optional) The category of check. Defaults to 'warning'.
    * @param int $priority
    *   (optional) The priority of the checker being added. Defaults to 0.
    *   Readiness checkers with larger priorities will run first within a
@@ -53,7 +53,7 @@ public function run(): array;
    *   An array of translatable messages if any checks fail, otherwise an empty
    *   array.
    */
-  public function getResults($category): array;
+  public function getResults(string $category): array;
 
   /**
    * Gets the timestamp of the most recent run.
diff --git a/core/modules/auto_updates/tests/modules/auto_updates_test/src/Datetime/TestTime.php b/core/modules/auto_updates/tests/modules/auto_updates_test/src/Datetime/TestTime.php
index 3bbc9d606a..3b86be5058 100644
--- a/core/modules/auto_updates/tests/modules/auto_updates_test/src/Datetime/TestTime.php
+++ b/core/modules/auto_updates/tests/modules/auto_updates_test/src/Datetime/TestTime.php
@@ -9,16 +9,22 @@
  */
 class TestTime extends Time {
 
+  /**
+   * The time format to for setting the test time.
+   */
   const TIME_FORMAT = 'U';
 
+  /**
+   * The state key for setting and getting the test time.
+   */
   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, $mock_date)->getTimestamp();
+    if ($faked_date = \Drupal::state()->get(TestTime::STATE_KEY)) {
+      return \DateTime::createFromFormat(self::TIME_FORMAT, $faked_date)->getTimestamp();
     }
     return parent::getRequestTime();
   }
diff --git a/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
index 1641cd468f..eed3815139 100644
--- a/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
@@ -6,19 +6,22 @@
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 
 /**
- * The disk space readiness checker.
+ * A test readiness checker.
  */
 class TestChecker implements ReadinessCheckerInterface {
 
   use StringTranslationTrait;
 
+  /**
+   * The state key for setting and getting checker message.
+   */
   const STATE_KEY = 'auto_updates_test.check_error';
 
   /**
    * {@inheritDoc}
    */
   public function run(): array {
-    if ($message = \Drupal::state()->get(static::STATE_KEY, NULL)) {
+    if ($message = \Drupal::state()->get(static::STATE_KEY)) {
       return [$message];
     }
     return [];