diff --git a/core/phpcs.xml.dist b/core/phpcs.xml.dist
index 9b9bc8bd92c112fb5c5f5119799c3bc38248d9bd..6953a1ad1ec84407719399dc1a6bca136f9877ff 100644
--- a/core/phpcs.xml.dist
+++ b/core/phpcs.xml.dist
@@ -85,6 +85,7 @@
   <rule ref="Drupal.Commenting.FunctionComment.MissingReturnComment">
     <include-pattern>core/lib/Drupal/Core/*</include-pattern>
     <include-pattern>core/lib/Drupal/Component/*</include-pattern>
+    <include-pattern>core/tests/*</include-pattern>
   </rule>
   <rule ref="Drupal.Commenting.FunctionComment.MissingReturnComment">
     <exclude-pattern>core/lib/Drupal/Core/*</exclude-pattern>
diff --git a/core/tests/Drupal/BuildTests/Framework/BuildTestBase.php b/core/tests/Drupal/BuildTests/Framework/BuildTestBase.php
index 313c6f54fa9d07eb3af8eddcbca060d98f8172ca..e92c75468843495af7751335d3e7798bd27b8de7 100644
--- a/core/tests/Drupal/BuildTests/Framework/BuildTestBase.php
+++ b/core/tests/Drupal/BuildTests/Framework/BuildTestBase.php
@@ -223,6 +223,7 @@ protected function getWorkingPath($working_dir = NULL) {
    * Set up the Mink session manager.
    *
    * @return \Behat\Mink\Session
+   *   The Mink session.
    */
   protected function initMink() {
     $client = new DrupalTestBrowser();
@@ -327,6 +328,7 @@ public function assertCommandExitCode($expected_code) {
    *   execute the command. Defaults to the workspace directory.
    *
    * @return \Symfony\Component\Process\Process
+   *   The process object.
    */
   public function executeCommand($command_line, $working_dir = NULL) {
     $this->commandProcess = Process::fromShellCommandline($command_line);
@@ -510,6 +512,7 @@ protected function findAvailablePort(): int {
    *   A number between 1024 and 65536.
    *
    * @return bool
+   *   TRUE if the port is available, FALSE otherwise.
    */
   protected function checkPortIsAvailable($port): bool {
     $fp = @fsockopen(self::$hostName, $port, $errno, $errstr, 1);
@@ -531,6 +534,7 @@ protected function checkPortIsAvailable($port): bool {
    * Test should never call this. Used by standUpServer().
    *
    * @return int
+   *   The port number.
    */
   protected function getPortNumber(): int {
     if (empty($this->hostPort)) {
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/MachineName/MachineNameTransliterationTest.php b/core/tests/Drupal/FunctionalJavascriptTests/MachineName/MachineNameTransliterationTest.php
index 3d4483a4f3a61c8a4691bf8d95ea4920c0402fa6..ad9ba4f89d8e8fa205f140c0a77fad4f947ba5b9 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/MachineName/MachineNameTransliterationTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/MachineName/MachineNameTransliterationTest.php
@@ -66,6 +66,8 @@ public function testMachineNameTransliterations($langcode, $input, $output): voi
    * Data for the testMachineNameTransliterations.
    *
    * @return array
+   *   An array of arrays, where each sub-array contains a language code,
+   *   input string, and the expected transliterated output string.
    */
   public static function machineNameInputOutput(): array {
     return [
diff --git a/core/tests/Drupal/FunctionalTests/DefaultContent/ContentImportTest.php b/core/tests/Drupal/FunctionalTests/DefaultContent/ContentImportTest.php
index 8a3078733c509ebfc67564a243d3b5fad8b1419d..06de4e64394d314836c403bda98557b40af93bfa 100644
--- a/core/tests/Drupal/FunctionalTests/DefaultContent/ContentImportTest.php
+++ b/core/tests/Drupal/FunctionalTests/DefaultContent/ContentImportTest.php
@@ -127,6 +127,7 @@ protected function setUp(): void {
 
   /**
    * @return array<array<mixed>>
+   *   An array of test cases, each containing an existing entity handling mode.
    */
   public static function providerImportEntityThatAlreadyExists(): array {
     return [
diff --git a/core/tests/Drupal/KernelTests/Component/Render/FormattableMarkupKernelTest.php b/core/tests/Drupal/KernelTests/Component/Render/FormattableMarkupKernelTest.php
index 104294b393987aaf534e37a5a022f90f1fe1b855..68d749ad92162098bda08829a42d4e9b16680990 100644
--- a/core/tests/Drupal/KernelTests/Component/Render/FormattableMarkupKernelTest.php
+++ b/core/tests/Drupal/KernelTests/Component/Render/FormattableMarkupKernelTest.php
@@ -51,6 +51,7 @@ public function testFormattableMarkupUri($string, $uri, $options, $expected): vo
 
   /**
    * @return array
+   *   Data provider for testFormattableMarkupUri().
    */
   public static function providerTestFormattableMarkupUri() {
     $data = [];
@@ -113,6 +114,7 @@ public function testFormattableMarkupUriWithExceptionUri($string, $uri): void {
 
   /**
    * @return array
+   *   Data provider for testFormattableMarkupUriWithExceptionUri().
    */
   public static function providerTestFormattableMarkupUriWithException() {
     $data = [];
diff --git a/core/tests/Drupal/KernelTests/Config/Schema/MappingTest.php b/core/tests/Drupal/KernelTests/Config/Schema/MappingTest.php
index f405783ceb182c5c2a2a166069d6c1464e7ab179..cd0f2473bdc363290acc9c27de9fa80336ba5bc3 100644
--- a/core/tests/Drupal/KernelTests/Config/Schema/MappingTest.php
+++ b/core/tests/Drupal/KernelTests/Config/Schema/MappingTest.php
@@ -167,6 +167,7 @@ public function testMappingInterpretation(
    * @see https://www.drupal.org/files/ConfigSchemaCheatSheet2.0.pdf
    *
    * @return \Generator
+   *   The test cases.
    */
   public static function providerMappingInterpretation(): \Generator {
     $available_block_settings_types = [
diff --git a/core/tests/Drupal/KernelTests/Core/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php b/core/tests/Drupal/KernelTests/Core/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
index b4fdc8fc853860d3a034b42e811dca0cca848402..340dcc28649457fcc868d6b7879c7e481657f8be 100644
--- a/core/tests/Drupal/KernelTests/Core/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
@@ -204,6 +204,7 @@ protected function verifyLibraryFilesExist($library_definitions): void {
    * Gets all libraries for core and all installed modules.
    *
    * @return \Drupal\Core\Extension\Extension[]
+   *   An array of discovered libraries keyed by extension name.
    */
   protected function getAllLibraries() {
     $modules = \Drupal::moduleHandler()->getModuleList();
diff --git a/core/tests/Drupal/KernelTests/Core/Config/ConfigEntityValidationTestBase.php b/core/tests/Drupal/KernelTests/Core/Config/ConfigEntityValidationTestBase.php
index 846405cf508cfe6bbc565772df57ac9527818714..18cd991e38d8a30d35783c1bcfe51dab56152249 100644
--- a/core/tests/Drupal/KernelTests/Core/Config/ConfigEntityValidationTestBase.php
+++ b/core/tests/Drupal/KernelTests/Core/Config/ConfigEntityValidationTestBase.php
@@ -496,6 +496,7 @@ public function testImmutableProperties(array $valid_values = []): void {
    * @todo Remove this optional parameter in https://www.drupal.org/project/drupal/issues/2820364#comment-15333069
    *
    * @return void
+   *   No return value.
    */
   public function testRequiredPropertyKeysMissing(?array $additional_expected_validation_errors_when_missing = NULL): void {
     $config_entity_properties = array_keys($this->entity->getEntityType()->getPropertiesToExport());
@@ -541,6 +542,7 @@ public function testRequiredPropertyKeysMissing(?array $additional_expected_vali
    * @todo Remove this optional parameter in https://www.drupal.org/project/drupal/issues/2820364#comment-15333069
    *
    * @return void
+   *   No return value.
    */
   public function testRequiredPropertyValuesMissing(?array $additional_expected_validation_errors_when_missing = NULL): void {
     $config_entity_properties = array_keys($this->entity->getEntityType()->getPropertiesToExport());
diff --git a/core/tests/Drupal/KernelTests/Core/Database/DriverSpecificConnectionUnitTestBase.php b/core/tests/Drupal/KernelTests/Core/Database/DriverSpecificConnectionUnitTestBase.php
index 596debea8bbae4b84b57e03fccf37fd18627858e..2af1bec7d0dc4693f2f4a84704203cb177141f3c 100644
--- a/core/tests/Drupal/KernelTests/Core/Database/DriverSpecificConnectionUnitTestBase.php
+++ b/core/tests/Drupal/KernelTests/Core/Database/DriverSpecificConnectionUnitTestBase.php
@@ -68,6 +68,7 @@ abstract protected function getQuery(): array;
    * Returns the connection ID of the current test connection.
    *
    * @return int
+   *   The connection ID.
    */
   protected function getConnectionId(): int {
     return (int) Database::getConnection(static::TEST_TARGET_CONNECTION)->query($this->getQuery()['connection_id'])->fetchField();
diff --git a/core/tests/Drupal/KernelTests/Core/DrupalKernel/DrupalKernelTest.php b/core/tests/Drupal/KernelTests/Core/DrupalKernel/DrupalKernelTest.php
index 343b9f19630dd290cd7794177bd89e7797e20ce3..3be9b023b2f79d08b86cd6d553bc5168efc88afd 100644
--- a/core/tests/Drupal/KernelTests/Core/DrupalKernel/DrupalKernelTest.php
+++ b/core/tests/Drupal/KernelTests/Core/DrupalKernel/DrupalKernelTest.php
@@ -205,6 +205,8 @@ public function testPreventChangeOfSitePath(): void {
    * Data provider for self::testClassLoaderAutoDetect.
    *
    * @return array
+   *   An array of test cases. Each test case is an array containing a single boolean value
+   *   that represents the class_loader_auto_detect setting to be tested.
    */
   public static function providerClassLoaderAutoDetect() {
     return [
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntityFieldTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityFieldTest.php
index 5e43c0bea2c5cd1c248af09bb714556e510b6e41..1c65e7f96429400aee49b90ce04b29adf012678c 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/EntityFieldTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityFieldTest.php
@@ -79,6 +79,7 @@ protected function setUp(): void {
    * Creates a test entity.
    *
    * @return \Drupal\Core\Entity\EntityInterface
+   *   The created entity.
    */
   protected function createTestEntity($entity_type): EntityInterface {
     $this->entityName = $this->randomMachineName();
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntityTypeTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityTypeTest.php
index 270c1c8f71f8a8be220da4168d15604903cf5478..260ada5cc795df97b8c63ada30ea8ea71ac17ab5 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/EntityTypeTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityTypeTest.php
@@ -22,6 +22,7 @@ class EntityTypeTest extends KernelTestBase {
    *   An array of values to use for the EntityType.
    *
    * @return \Drupal\Core\Entity\EntityTypeInterface
+   *   The EntityType object.
    */
   protected function setUpEntityType($definition) {
     $definition += [
diff --git a/core/tests/Drupal/KernelTests/Core/Routing/ExceptionHandlingTest.php b/core/tests/Drupal/KernelTests/Core/Routing/ExceptionHandlingTest.php
index 1c2944a18ed73b71da6231dadf8938ebd961a754..286995f04498262eb4e04af45cd0cf27a9d426f8 100644
--- a/core/tests/Drupal/KernelTests/Core/Routing/ExceptionHandlingTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Routing/ExceptionHandlingTest.php
@@ -146,6 +146,7 @@ public function testExceptionResponseGeneratedForOriginalRequest(): void {
    *   The path to test.
    *
    * @return \Drupal\Core\Render\HtmlResponse
+   *   The generated 404 response.
    *
    * @see \Drupal\system\Tests\Routing\ExceptionHandlingTest::testExceptionResponseGeneratedForOriginalRequest()
    */
diff --git a/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php b/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
index 3ef3ec815dd404f126c812538a70c608adfdc117..df7204d5f74b6c3cd98b9acfa3fd97f71d7dc145 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
@@ -453,6 +453,7 @@ public function testThemeInfoAlter(): void {
    * Returns the theme handler service.
    *
    * @return \Drupal\Core\Extension\ThemeHandlerInterface
+   *   The theme handler service.
    */
   protected function themeHandler() {
     return $this->container->get('theme_handler');
@@ -462,6 +463,7 @@ protected function themeHandler() {
    * Returns the theme installer service.
    *
    * @return \Drupal\Core\Extension\ThemeInstallerInterface
+   *   The theme installer service.
    */
   protected function themeInstaller() {
     return $this->container->get('theme_installer');
@@ -471,6 +473,7 @@ protected function themeInstaller() {
    * Returns the system.theme config object.
    *
    * @return \Drupal\Core\Config\Config
+   *   The system.theme config object.
    */
   protected function extensionConfig() {
     return $this->config('core.extension');
@@ -480,6 +483,7 @@ protected function extensionConfig() {
    * Returns the ModuleHandler.
    *
    * @return \Drupal\Core\Extension\ModuleHandlerInterface
+   *   The ModuleHandler.
    */
   protected function moduleHandler(): ?object {
     return $this->container->get('module_handler');
@@ -489,6 +493,7 @@ protected function moduleHandler(): ?object {
    * Returns the ModuleInstaller.
    *
    * @return \Drupal\Core\Extension\ModuleInstallerInterface
+   *   The ModuleInstaller.
    */
   protected function moduleInstaller(): ?object {
     return $this->container->get('module_installer');
@@ -498,6 +503,7 @@ protected function moduleInstaller(): ?object {
    * Returns the ThemeExtensionList.
    *
    * @return \Drupal\Core\Extension\ThemeExtensionList
+   *   The ThemeExtensionList.
    */
   protected function extensionListTheme(): ThemeExtensionList {
     return $this->container->get('extension.list.theme');
diff --git a/core/tests/Drupal/KernelTests/KernelTestBase.php b/core/tests/Drupal/KernelTests/KernelTestBase.php
index 843ec4a3999d6a4171f63b09efd4a544905cc072..bedc836e0f9ee9e1e6e66f04de1b586726696969 100644
--- a/core/tests/Drupal/KernelTests/KernelTestBase.php
+++ b/core/tests/Drupal/KernelTests/KernelTestBase.php
@@ -296,6 +296,7 @@ protected function setUpFilesystem() {
 
   /**
    * @return string
+   *   The database prefix string used to isolate test database tables.
    */
   public function getDatabasePrefix() {
     return $this->databasePrefix;
@@ -971,6 +972,7 @@ protected function vfsDump() {
    *   The fully-qualified class name of this test.
    *
    * @return array
+   *   An array of modules to install.
    */
   private static function getModulesToEnable($class) {
     $modules = [];
diff --git a/core/tests/Drupal/TestTools/Extension/InfoWriterTrait.php b/core/tests/Drupal/TestTools/Extension/InfoWriterTrait.php
index a604a1583c941a8152b0160a3bf8def9c7b81350..47680a362a0f2cfdc53f9d42cdeb65ce12222088 100644
--- a/core/tests/Drupal/TestTools/Extension/InfoWriterTrait.php
+++ b/core/tests/Drupal/TestTools/Extension/InfoWriterTrait.php
@@ -23,6 +23,7 @@ trait InfoWriterTrait {
    *   The info array.
    *
    * @return void
+   *   No return value.
    */
   private function writeInfoFile(string $file_path, array $info): void {
     $mtime = file_exists($file_path) ? filemtime($file_path) : FALSE;
diff --git a/core/tests/Drupal/Tests/Component/Datetime/TimeTest.php b/core/tests/Drupal/Tests/Component/Datetime/TimeTest.php
index f793e3a9460d9e3ccbfce23e3bd2e0defd48e8b1..c09a46d6116c4cf45600935086a3f54543a37f9c 100644
--- a/core/tests/Drupal/Tests/Component/Datetime/TimeTest.php
+++ b/core/tests/Drupal/Tests/Component/Datetime/TimeTest.php
@@ -134,6 +134,7 @@ public function testGetCurrentMicroTime(): void {
  * Shadow time() system call.
  *
  * @return int
+ *   The fixed integer timestamp used for testing purposes.
  */
 function time() {
   return 12345678;
@@ -143,6 +144,7 @@ function time() {
  * Shadow microtime system call.
  *
  * @return float
+ *   The fixed float timestamp used for testing purposes.
  */
 function microtime(bool $as_float = FALSE) {
   return 1234567.89;
diff --git a/core/tests/Drupal/Tests/Component/DrupalComponentTest.php b/core/tests/Drupal/Tests/Component/DrupalComponentTest.php
index e6260eead05d1b80c824614e6887ffb50d934fc1..4ffa430c05b56e831a4b0334e18e96ef90901825 100644
--- a/core/tests/Drupal/Tests/Component/DrupalComponentTest.php
+++ b/core/tests/Drupal/Tests/Component/DrupalComponentTest.php
@@ -52,6 +52,8 @@ public function testComponentLicense(string $component_path): void {
    * Data provider.
    *
    * @return array
+   *   An associative array where the keys are component names and the values
+   *   are arrays containing the corresponding component path.
    */
   public static function getComponents(): array {
     $root_component_path = dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))) . '/lib/Drupal/Component';
diff --git a/core/tests/Drupal/Tests/Component/Plugin/PluginBaseTest.php b/core/tests/Drupal/Tests/Component/Plugin/PluginBaseTest.php
index 51ff3575f96982b28bcf6a26c33c665ff58115b0..42aa7863f2dac6f2a73ca3d154301d2b7931e487 100644
--- a/core/tests/Drupal/Tests/Component/Plugin/PluginBaseTest.php
+++ b/core/tests/Drupal/Tests/Component/Plugin/PluginBaseTest.php
@@ -30,6 +30,8 @@ public function testGetPluginId($plugin_id, $expected): void {
    * Returns test data for testGetPluginId().
    *
    * @return array
+   *   An array of test cases, where each item contains a plugin ID and
+   *   the expected plugin ID result.
    */
   public static function providerTestGetPluginId() {
     return [
@@ -56,6 +58,8 @@ public function testGetBaseId($plugin_id, $expected): void {
    * Returns test data for testGetBaseId().
    *
    * @return array
+   *   An array of test cases, where each item contains a plugin ID and
+   *   the expected base ID result.
    */
   public static function providerTestGetBaseId() {
     return [
@@ -82,6 +86,8 @@ public function testGetDerivativeId($plugin_id = NULL, $expected = NULL): void {
    * Returns test data for testGetDerivativeId().
    *
    * @return array
+   *   An array of test cases, where each item contains a plugin ID and
+   *   the expected derivative ID result.
    */
   public static function providerTestGetDerivativeId() {
     return [
diff --git a/core/tests/Drupal/Tests/Component/Render/FormattableMarkupTest.php b/core/tests/Drupal/Tests/Component/Render/FormattableMarkupTest.php
index 7962148796e07109789d8b903ee1aa8481153459..5120d0e78c0e35542d4f5db773771321de6ea75e 100644
--- a/core/tests/Drupal/Tests/Component/Render/FormattableMarkupTest.php
+++ b/core/tests/Drupal/Tests/Component/Render/FormattableMarkupTest.php
@@ -93,6 +93,7 @@ public function testUnexpectedPlaceholder($string, $arguments, $error_number, $e
    * Data provider for FormattableMarkupTest::testUnexpectedPlaceholder().
    *
    * @return array
+   *   An array of test cases.
    */
   public static function providerTestUnexpectedPlaceholder() {
     return [
diff --git a/core/tests/Drupal/Tests/Component/Utility/CryptTest.php b/core/tests/Drupal/Tests/Component/Utility/CryptTest.php
index 8dcc87f4462e880bd11fe0850e70f09378d2578c..7aff98aab423afaf45705975292eee9e417eba3f 100644
--- a/core/tests/Drupal/Tests/Component/Utility/CryptTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/CryptTest.php
@@ -69,7 +69,10 @@ public function testHmacBase64Invalid($data, $key): void {
   /**
    * Provides data for self::testHashBase64().
    *
-   * @return array Test data.
+   * @return array
+   *   An array of test cases. Each test case contains:
+   *   - string $data: The input string to hash.
+   *   - string $expected_hash: The expected Base64-encoded hash value.
    */
   public static function providerTestHashBase64() {
     return [
@@ -89,7 +92,11 @@ public static function providerTestHashBase64() {
   /**
    * Provides data for self::testHmacBase64().
    *
-   * @return array Test data.
+   * @return array
+   *   An array of test cases. Each test case contains:
+   *   - string $data: The input string to hash.
+   *   - string $key: The key to use in the hashing process.
+   *   - string $expected_hmac: The expected Base64-encoded HMAC value.
    */
   public static function providerTestHmacBase64() {
     return [
@@ -105,7 +112,10 @@ public static function providerTestHmacBase64() {
   /**
    * Provides data for self::testHmacBase64().
    *
-   * @return array Test data.
+   * @return array
+   *   An array of test cases. Each test case contains:
+   *   - string $data: The input string to hash.
+   *   - string $key: The key to use in the hashing process.
    */
   public static function providerTestHmacBase64Invalid() {
     return [
diff --git a/core/tests/Drupal/Tests/Component/Utility/ReflectionTest.php b/core/tests/Drupal/Tests/Component/Utility/ReflectionTest.php
index c1ea6045939eedd6e21d5fb824b67182ed2b9f18..4a0a6fb4b8540c88d3df036c3c97c59f9a1f5c17 100644
--- a/core/tests/Drupal/Tests/Component/Utility/ReflectionTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/ReflectionTest.php
@@ -30,6 +30,9 @@ public function testGetParameterClassName(?string $expected, \ReflectionParamete
    * Data provider for ::testGetParameterClassName().
    *
    * @return array[]
+   *   An array of test cases. Each test case is an associative array containing:
+   *   - string|null $expected: The expected class name.
+   *   - \ReflectionParameter $parameter: The reflection parameter.
    */
   public static function providerGetParameterClassName() {
     $reflection_method = new \ReflectionMethod(static::class, 'existsForTesting');
diff --git a/core/tests/Drupal/Tests/Component/Utility/UrlHelperTest.php b/core/tests/Drupal/Tests/Component/Utility/UrlHelperTest.php
index 8e77ae27467abbdd6083ed2d7be945731c0c3ce4..158e626c821301afe77e48226b5681bd33a93f7d 100644
--- a/core/tests/Drupal/Tests/Component/Utility/UrlHelperTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/UrlHelperTest.php
@@ -18,6 +18,10 @@ class UrlHelperTest extends TestCase {
    * Provides test data for testBuildQuery().
    *
    * @return array
+   *   An array of test cases. Each test case contains:
+   *   - array $query: An array of query parameters.
+   *   - string $expected: The expected query string.
+   *   - string $message: The assertion message.
    */
   public static function providerTestBuildQuery() {
     return [
@@ -50,6 +54,7 @@ public function testBuildQuery($query, $expected, $message): void {
    * Data provider for testValidAbsolute().
    *
    * @return array
+   *   An array of valid absolute URLs, with various schemes applied.
    */
   public static function providerTestValidAbsoluteData(): array {
     $urls = [
@@ -99,6 +104,7 @@ public function testValidAbsolute(string $url, string $scheme): void {
    * Provides data for testInvalidAbsolute().
    *
    * @return array
+   *   An array of invalid absolute URLs.
    */
   public static function providerTestInvalidAbsolute(): array {
     $data = [
@@ -154,6 +160,7 @@ public function testInvalidAbsolute(string $url, string $scheme): void {
    * Provides data for testValidRelative().
    *
    * @return array
+   *   An array of valid relative URLs.
    */
   public static function providerTestValidRelativeData(): array {
     $data = [
@@ -188,6 +195,7 @@ public function testValidRelative(string $url, string $prefix): void {
    * Provides data for testInvalidRelative().
    *
    * @return array
+   *   An array of invalid relative URLs.
    */
   public static function providerTestInvalidRelativeData(): array {
     $data = [
@@ -239,8 +247,9 @@ public function testFilterQueryParameters($query, $exclude, $expected): void {
    * Provides data to self::testFilterQueryParameters().
    *
    * @return array
+   *   An array of test cases with query parameters, exclusions, and expected results.
    */
-  public static function providerTestFilterQueryParameters() {
+  public static function providerTestFilterQueryParameters(): array {
     return [
       // Test without an exclude filter.
       [
@@ -277,6 +286,7 @@ public function testParse($url, $expected): void {
    * Provides data for self::testParse().
    *
    * @return array
+   *   An array of test cases with URLs and expected parsed results.
    */
   public static function providerTestParse() {
     return [
@@ -399,6 +409,7 @@ public function testEncodePath($path, $expected): void {
    * Provides data for self::testEncodePath().
    *
    * @return array
+   *   An array of test cases with unencoded paths and expected encoded paths.
    */
   public static function providerTestEncodePath() {
     return [
@@ -427,6 +438,7 @@ public function testIsExternal($path, $expected): void {
    * Provides data for self::testIsExternal().
    *
    * @return array
+   *   An array of test cases with paths and their expected external status.
    */
   public static function providerTestIsExternal() {
     return [
@@ -491,6 +503,7 @@ public function testFilterBadProtocol($uri, $expected, $protocols): void {
    * Provides data for self::testTestFilterBadProtocol().
    *
    * @return array
+   *   An array of test cases with URIs, expected filtered results, and allowed protocols.
    */
   public static function providerTestFilterBadProtocol() {
     return [
@@ -529,6 +542,7 @@ public function testStripDangerousProtocols($uri, $expected, $protocols): void {
    * Provides data for self::testStripDangerousProtocols().
    *
    * @return array
+   *   An array of test cases with URIs, expected stripped results, and allowed protocols.
    */
   public static function providerTestStripDangerousProtocols() {
     return [
diff --git a/core/tests/Drupal/Tests/Component/Uuid/UuidTest.php b/core/tests/Drupal/Tests/Component/Uuid/UuidTest.php
index a0c2dd8b9cda3bb21fcfa3c7e0b6007f8e95c552..1d1f0b4023229f5ae23e4433597e3f0f8bb3839a 100644
--- a/core/tests/Drupal/Tests/Component/Uuid/UuidTest.php
+++ b/core/tests/Drupal/Tests/Component/Uuid/UuidTest.php
@@ -40,6 +40,7 @@ public function testUuidIsUnique(UuidInterface $instance): void {
    * Data provider for UUID instance tests.
    *
    * @return array
+   *   An array of UUID generator instances.
    */
   public static function providerUuidInstances() {
 
diff --git a/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/ScaffoldTestResult.php b/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/ScaffoldTestResult.php
index f474e95074c2bcc224261abcfc7b76e65566f482..e8b009c5c38ade1df29e6bba624f4e7a3603f39f 100644
--- a/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/ScaffoldTestResult.php
+++ b/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/ScaffoldTestResult.php
@@ -40,6 +40,7 @@ public function __construct($docroot, $scaffoldOutput) {
    * Returns the location of the docroot from the scaffold test.
    *
    * @return string
+   *   The location of the scaffold fixture.
    */
   public function docroot() {
     return $this->docroot;
@@ -49,6 +50,7 @@ public function docroot() {
    * Returns the standard output from the scaffold test.
    *
    * @return string
+   *   The standard output from the scaffold test.
    */
   public function scaffoldOutput() {
     return $this->scaffoldOutput;
diff --git a/core/tests/Drupal/Tests/ComposerIntegrationTest.php b/core/tests/Drupal/Tests/ComposerIntegrationTest.php
index 69e3517e775397d35e67adac5509d58acb9a220a..f3634f8ee38272bd10e6c416005ec1110265af6f 100644
--- a/core/tests/Drupal/Tests/ComposerIntegrationTest.php
+++ b/core/tests/Drupal/Tests/ComposerIntegrationTest.php
@@ -77,6 +77,7 @@ public function testComposerTilde(string $path): void {
    * Data provider for all the composer.json provided by Drupal core.
    *
    * @return array
+   *   An array of composer.json file paths.
    */
   public static function providerTestComposerJson(): array {
     $data = [];
@@ -134,6 +135,7 @@ public function testAllCoreComponentsReplaced(): void {
    * Data provider for the scaffold files test for Drupal core.
    *
    * @return array
+   *   An array of scaffold file mappings.
    */
   public static function providerTestExpectedScaffoldFiles() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Access/AccessManagerTest.php b/core/tests/Drupal/Tests/Core/Access/AccessManagerTest.php
index fe6222df3cefcac84a366582349622570ef930e6..913f83004e8c6eda34b59d0b125761cbccab0238 100644
--- a/core/tests/Drupal/Tests/Core/Access/AccessManagerTest.php
+++ b/core/tests/Drupal/Tests/Core/Access/AccessManagerTest.php
@@ -506,6 +506,7 @@ public function testCheckException($return_value): void {
    * Data provider for testCheckException.
    *
    * @return array
+   *   An array of data for check exceptions.
    */
   public static function providerCheckException() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Access/AccessResultTest.php b/core/tests/Drupal/Tests/Core/Access/AccessResultTest.php
index 5ae1dddc7672087eb688c0daec422e944fc8a618..7d06831a40b4dd35f484dccdaa65ac4b08b60334 100644
--- a/core/tests/Drupal/Tests/Core/Access/AccessResultTest.php
+++ b/core/tests/Drupal/Tests/Core/Access/AccessResultTest.php
@@ -940,6 +940,7 @@ public function testAllowedIfHasPermissions($permissions, $conjunction, AccessRe
    * Provides data for the testAllowedIfHasPermissions() method.
    *
    * @return array
+   *   An array of test scenarios with permissions, logic, and expected result.
    */
   public static function providerTestAllowedIfHasPermissions() {
     $access_result = AccessResult::allowedIf(FALSE);
diff --git a/core/tests/Drupal/Tests/Core/Ajax/OpenOffCanvasDialogCommandTest.php b/core/tests/Drupal/Tests/Core/Ajax/OpenOffCanvasDialogCommandTest.php
index 5065b543e9f9b785ff4c1435aba7d7fe41c0ca94..3f607877c66f4edf5619ee6811e6c981e9b8a914 100644
--- a/core/tests/Drupal/Tests/Core/Ajax/OpenOffCanvasDialogCommandTest.php
+++ b/core/tests/Drupal/Tests/Core/Ajax/OpenOffCanvasDialogCommandTest.php
@@ -51,6 +51,7 @@ public function testRender($position): void {
    * The data provider for potential dialog positions.
    *
    * @return array
+   *   An array of dialog positions.
    */
   public static function dialogPosition() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Cache/CacheTest.php b/core/tests/Drupal/Tests/Core/Cache/CacheTest.php
index dc005bc3f0926f75604a1d4c0a4ca9d40164349a..2290e76f492cc2ec7fab24a3aef906cf9b9ddfa1 100644
--- a/core/tests/Drupal/Tests/Core/Cache/CacheTest.php
+++ b/core/tests/Drupal/Tests/Core/Cache/CacheTest.php
@@ -20,6 +20,7 @@ class CacheTest extends UnitTestCase {
    * Provides a list of cache tags arrays.
    *
    * @return array
+   *   An array of cache tags arrays.
    */
   public function validateTagsProvider() {
     return [
@@ -49,6 +50,7 @@ public function validateTagsProvider() {
    * Provides a list of pairs of cache tags arrays to be merged.
    *
    * @return array
+   *   An array of pairs of cache tags arrays to be merged.
    */
   public static function mergeTagsProvider() {
     return [
@@ -76,6 +78,7 @@ public function testMergeTags(array $expected, ...$cache_tags): void {
    * Provides a list of pairs of cache tags arrays to be merged.
    *
    * @return array
+   *   An array of pairs of cache tags arrays to be merged.
    */
   public static function mergeMaxAgesProvider() {
     return [
@@ -115,6 +118,7 @@ public function testMergeMaxAges($expected, ...$max_ages): void {
    * Provides a list of pairs of cache contexts arrays to be merged.
    *
    * @return array
+   *   An array of pairs of cache contexts arrays to be merged.
    */
   public static function mergeCacheContextsProvide() {
     return [
@@ -154,6 +158,7 @@ public function testMergeCacheContexts(array $expected, ...$contexts): void {
    * Provides a list of pairs of (prefix, suffixes) to build cache tags from.
    *
    * @return array
+   *   An array of pairs of (prefix, suffixes) to build cache tags from.
    */
   public static function buildTagsProvider() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Cache/CacheableMetadataTest.php b/core/tests/Drupal/Tests/Core/Cache/CacheableMetadataTest.php
index 9162ecf21cd5df4facfce32f5cb744bd8518852b..a4119bab9d1f1d7ee5bae5f53064a2d9531d1b73 100644
--- a/core/tests/Drupal/Tests/Core/Cache/CacheableMetadataTest.php
+++ b/core/tests/Drupal/Tests/Core/Cache/CacheableMetadataTest.php
@@ -71,6 +71,7 @@ public function testAddCacheableDependency(CacheableMetadata $a, CacheableMetada
    * Provides test data for testMerge().
    *
    * @return array
+   *   An array of test cases, each containing two CacheableMetadata objects and their expected merged result.
    */
   public static function providerTestMerge() {
     return [
@@ -150,6 +151,7 @@ public function testCreateFromRenderArray(array $render_array, CacheableMetadata
    * Provides test data for createFromRenderArray().
    *
    * @return array
+   *   An array of test cases, each containing a render array and the expected CacheableMetadata object.
    */
   public static function providerTestCreateFromRenderArray() {
     $data = [];
@@ -186,6 +188,7 @@ public function testCreateFromObject($object, CacheableMetadata $expected): void
    * Provides test data for createFromObject().
    *
    * @return array
+   *   An array of test cases, each containing an object and the expected CacheableMetadata.
    */
   public static function providerTestCreateFromObject() {
     $data = [];
diff --git a/core/tests/Drupal/Tests/Core/Cache/Context/CacheContextsManagerTest.php b/core/tests/Drupal/Tests/Core/Cache/Context/CacheContextsManagerTest.php
index 042c2749044016fa5e7952047bd00d99f6254371..f76e8cd647437b76f5439c538852311260360b5e 100644
--- a/core/tests/Drupal/Tests/Core/Cache/Context/CacheContextsManagerTest.php
+++ b/core/tests/Drupal/Tests/Core/Cache/Context/CacheContextsManagerTest.php
@@ -199,6 +199,7 @@ protected function getMockContainer() {
    * Provides a list of cache context token arrays.
    *
    * @return array
+   *   An array of cache context token arrays.
    */
   public static function validateTokensProvider() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Cache/Context/IsFrontPathCacheContextTest.php b/core/tests/Drupal/Tests/Core/Cache/Context/IsFrontPathCacheContextTest.php
index 5d4084b5b605cf53a7fb4ba624aa40a77d6e9c5e..2f80da3220726407af5f803c5cb49c3cdd6209c0 100644
--- a/core/tests/Drupal/Tests/Core/Cache/Context/IsFrontPathCacheContextTest.php
+++ b/core/tests/Drupal/Tests/Core/Cache/Context/IsFrontPathCacheContextTest.php
@@ -38,6 +38,7 @@ public function testGetContextNotFront(): void {
    *   Whether the page is the front page.
    *
    * @return \Prophecy\Prophecy\ObjectProphecy<\Drupal\Core\Path\PathMatcherInterface>
+   *   The path matcher prophecy.
    */
   protected function createPathMatcher($is_front): ObjectProphecy {
     $path_matcher = $this->prophesize(PathMatcherInterface::class);
diff --git a/core/tests/Drupal/Tests/Core/Common/AttributesTest.php b/core/tests/Drupal/Tests/Core/Common/AttributesTest.php
index e051a1338bb311287b9adbd7a7b04c3e8505b4c9..6a65be7f0460fe0b3be5eef664db7f0d8a4f3722 100644
--- a/core/tests/Drupal/Tests/Core/Common/AttributesTest.php
+++ b/core/tests/Drupal/Tests/Core/Common/AttributesTest.php
@@ -18,6 +18,7 @@ class AttributesTest extends UnitTestCase {
    * Provides data for the Attribute test.
    *
    * @return array
+   *   An array of attributes, expected output, and descriptions.
    */
   public static function providerTestAttributeData() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php
index 03f1059d18260a3f66e510dcf4f20fe0f3a4cb7c..840dbc6a4383a9faa810cd59c298cd5b13da144a 100644
--- a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php
@@ -288,6 +288,7 @@ public function testCalculateDependenciesWithPluginCollections(array $definition
    * Data provider for testCalculateDependenciesWithPluginCollections.
    *
    * @return array
+   *   An array of test cases, each containing a plugin definition and expected dependencies.
    */
   public static function providerCalculateDependenciesWithPluginCollections(): array {
     // Start with 'a' so that order of the dependency array is fixed.
diff --git a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
index 0330e1b60b2af1e96e59c48cb0af1529372e9eea..2b4d2990d52efc4503e594430c69d7394eeb277c 100644
--- a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
@@ -198,6 +198,7 @@ public function testCreateWithPredefinedUuid(): void {
    * @covers ::doCreate
    *
    * @return \Drupal\Core\Entity\EntityInterface
+   *   The created entity with ID, language code, and UUID set.
    */
   public function testCreate() {
     $this->cacheTagsInvalidator->invalidateTags(Argument::cetera())->shouldNotBeCalled();
@@ -253,6 +254,7 @@ public function testCreateWithExplicitLanguage(): void {
    *   The entity to test.
    *
    * @return \Drupal\Core\Entity\EntityInterface
+   *   The saved entity after insertion.
    *
    * @depends testCreate
    */
@@ -306,6 +308,7 @@ public function testSaveInsert(EntityInterface $entity) {
    *   The entity to test.
    *
    * @return \Drupal\Core\Entity\EntityInterface
+   *   The saved entity after update.
    *
    * @depends testSaveInsert
    */
@@ -696,6 +699,7 @@ public function testDeleteNothing(): void {
    *   (optional) The methods to mock.
    *
    * @return \Drupal\Core\Config\Entity\ConfigEntityInterface&\PHPUnit\Framework\MockObject\MockObject
+   *   A mocked configuration entity instance.
    */
   public function getMockEntity(array $values = [], array $methods = []): ConfigEntityInterface&MockObject {
     return $this->getMockBuilder(StubConfigEntity::class)
diff --git a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityTypeTest.php b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityTypeTest.php
index b3b29d0d517200a0778cd9b4cacfa507146a9fa3..871af06c009781748907d2890aad3656f6ea9831 100644
--- a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityTypeTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityTypeTest.php
@@ -42,6 +42,7 @@ protected function setUp(): void {
    *   An array of values to use for the ConfigEntityType.
    *
    * @return \Drupal\Core\Config\Entity\ConfigEntityTypeInterface
+   *   The ConfigEntityType object.
    */
   protected function setUpConfigEntityType($definition) {
     if (!isset($definition['id'])) {
diff --git a/core/tests/Drupal/Tests/Core/Config/StorageCopyTraitTest.php b/core/tests/Drupal/Tests/Core/Config/StorageCopyTraitTest.php
index 8a64287ea0fde2730a8ef532f47fa63fdb119b12..7306794369238f56513396180feea0d4419d7eed 100644
--- a/core/tests/Drupal/Tests/Core/Config/StorageCopyTraitTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/StorageCopyTraitTest.php
@@ -85,6 +85,7 @@ public static function providerTestReplaceStorageContents() {
    *   The config storage to extract the data from.
    *
    * @return array
+   *   The config data as an array.
    */
   protected static function toArray(MemoryStorage $storage) {
     $reflection = new \ReflectionObject($storage);
diff --git a/core/tests/Drupal/Tests/Core/Database/ConditionTest.php b/core/tests/Drupal/Tests/Core/Database/ConditionTest.php
index 7ef2e4fd4fc0af915139a230c33f78b288d2eb54..8cdfffbac14ad1354ab9de2e3721ee11dacecaec 100644
--- a/core/tests/Drupal/Tests/Core/Database/ConditionTest.php
+++ b/core/tests/Drupal/Tests/Core/Database/ConditionTest.php
@@ -113,6 +113,7 @@ public function testCompileWithKnownOperators($expected, $field, $value, $operat
    * Provides a list of known operations and the expected output.
    *
    * @return array
+   *   An array of known operations and the expected output.
    */
   public static function dataProviderTestCompileWithKnownOperators() {
     // Below are a list of commented out test cases, which should work but
diff --git a/core/tests/Drupal/Tests/Core/Database/RowCountExceptionTest.php b/core/tests/Drupal/Tests/Core/Database/RowCountExceptionTest.php
index 411bec228eafaa0bb44ab9e3759e1c5d01a96e6f..7ecc4518d7140c4e2ff0b278ba945edd9907da9e 100644
--- a/core/tests/Drupal/Tests/Core/Database/RowCountExceptionTest.php
+++ b/core/tests/Drupal/Tests/Core/Database/RowCountExceptionTest.php
@@ -23,6 +23,7 @@ class RowCountExceptionTest extends UnitTestCase {
    * Data provider for ::testExceptionMessage()
    *
    * @return array
+   *   An array of test data for ::testExceptionMessage().
    */
   public static function providerTestExceptionMessage() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/DependencyInjection/Compiler/BackendCompilerPassTest.php b/core/tests/Drupal/Tests/Core/DependencyInjection/Compiler/BackendCompilerPassTest.php
index 0d8727710d3646cf15c10e1845acb3053ead4a9b..577c25c3ff9ed12ce224066c8a026486658abae7 100644
--- a/core/tests/Drupal/Tests/Core/DependencyInjection/Compiler/BackendCompilerPassTest.php
+++ b/core/tests/Drupal/Tests/Core/DependencyInjection/Compiler/BackendCompilerPassTest.php
@@ -104,6 +104,7 @@ public function testProcess(): void {
    *   The service definition.
    *
    * @return \Symfony\Component\DependencyInjection\ContainerBuilder
+   *   The container with a sqlite database service in it.
    */
   protected function getSqliteContainer($service) {
     $container = new ContainerBuilder();
@@ -124,6 +125,7 @@ protected function getSqliteContainer($service) {
    *   The service definition.
    *
    * @return \Symfony\Component\DependencyInjection\ContainerBuilder
+   *   The container with a mysql database service in it.
    */
   protected function getMysqlContainer($service) {
     $container = new ContainerBuilder();
@@ -142,6 +144,7 @@ protected function getMysqlContainer($service) {
    *   The service definition.
    *
    * @return \Symfony\Component\DependencyInjection\ContainerBuilder
+   *   The container with a DriverTestMysql database service in it.
    */
   protected function getDriverTestMysqlContainer($service) {
     $container = new ContainerBuilder();
diff --git a/core/tests/Drupal/Tests/Core/DependencyInjection/Compiler/StackedKernelPassTest.php b/core/tests/Drupal/Tests/Core/DependencyInjection/Compiler/StackedKernelPassTest.php
index 9f9e743050bea2233c693920896a1a6bf938ad4b..f8222587a007bbb680a8b6571e955cc24089bcbe 100644
--- a/core/tests/Drupal/Tests/Core/DependencyInjection/Compiler/StackedKernelPassTest.php
+++ b/core/tests/Drupal/Tests/Core/DependencyInjection/Compiler/StackedKernelPassTest.php
@@ -155,6 +155,7 @@ public function testProcessWithStackedKernelAndFinalHttpMiddleware(): void {
    *   The priority to be used for the tag.
    *
    * @return \Symfony\Component\DependencyInjection\Definition
+   *   The middleware definition.
    */
   protected function createMiddlewareServiceDefinition($tag = TRUE, $priority = 0) {
     $definition = new Definition('Symfony\Component\HttpKernel\HttpKernelInterface', ['test']);
diff --git a/core/tests/Drupal/Tests/Core/Entity/EntityCreateAccessCheckTest.php b/core/tests/Drupal/Tests/Core/Entity/EntityCreateAccessCheckTest.php
index f2868d22ab7f780f7912f5a957c1509b7c850627..dcfcd82b0370a65a4d94c6f78be58a1961fc4cf7 100644
--- a/core/tests/Drupal/Tests/Core/Entity/EntityCreateAccessCheckTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/EntityCreateAccessCheckTest.php
@@ -46,6 +46,7 @@ protected function setUp(): void {
    * Provides test data for testAccess.
    *
    * @return array
+   *   An array of test data for testAccess.
    */
   public static function providerTestAccess() {
     $no_access = FALSE;
diff --git a/core/tests/Drupal/Tests/Core/Entity/EntityTypeTest.php b/core/tests/Drupal/Tests/Core/Entity/EntityTypeTest.php
index c1217a722626468fa38429112a861305fc4cafa0..d810500b1a0eee019e5f63c5aa01fdbf7c9590ce 100644
--- a/core/tests/Drupal/Tests/Core/Entity/EntityTypeTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/EntityTypeTest.php
@@ -24,6 +24,7 @@ class EntityTypeTest extends UnitTestCase {
    *   An array of values to use for the EntityType.
    *
    * @return \Drupal\Core\Entity\EntityTypeInterface
+   *   The EntityType object.
    */
   protected function setUpEntityType($definition) {
     $definition += [
diff --git a/core/tests/Drupal/Tests/Core/Entity/EntityUrlTest.php b/core/tests/Drupal/Tests/Core/Entity/EntityUrlTest.php
index 41603ca4a6cc15731146236ddf725d7abead592d..79d46b05ac4be4ab722d13b1ebef7c381cc07654 100644
--- a/core/tests/Drupal/Tests/Core/Entity/EntityUrlTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/EntityUrlTest.php
@@ -472,6 +472,7 @@ public function testUriRelationships(): void {
    *   The getEntityType() and entityTypeBundleInfo() methods are always mocked.
    *
    * @return \Drupal\Tests\Core\Entity\StubEntityBase&\PHPUnit\Framework\MockObject\MockObject
+   *   A mock entity object with predefined methods and properties for testing.
    */
   protected function getEntity(string $class, array $values, array $methods = []): StubEntityBase&MockObject {
     $methods = array_merge($methods, ['getEntityType', 'entityTypeBundleInfo']);
diff --git a/core/tests/Drupal/Tests/Core/Entity/FieldDefinitionTest.php b/core/tests/Drupal/Tests/Core/Entity/FieldDefinitionTest.php
index 0ba944f287c6f776aff809b2777170f655b0c8cc..30e5d0917eb1d93ea20f5d422e8a93e6a4b4064c 100644
--- a/core/tests/Drupal/Tests/Core/Entity/FieldDefinitionTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/FieldDefinitionTest.php
@@ -368,6 +368,7 @@ public static function factoryTypeProvider() {
    *   The factory name to use.
    *
    * @return \Drupal\Core\Field\FieldDefinition
+   *   A field definition instance created using the specified factory.
    */
   protected function initializeFieldUsingFactory($factory_name) {
     switch ($factory_name) {
diff --git a/core/tests/Drupal/Tests/Core/Entity/KeyValueStore/KeyValueEntityStorageTest.php b/core/tests/Drupal/Tests/Core/Entity/KeyValueStore/KeyValueEntityStorageTest.php
index e82cd6885cbc2bef573cefa90ecafd75f0c7726a..7b17519f4108c6d064d767d1cfdf4536e542e295 100644
--- a/core/tests/Drupal/Tests/Core/Entity/KeyValueStore/KeyValueEntityStorageTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/KeyValueStore/KeyValueEntityStorageTest.php
@@ -208,6 +208,7 @@ public function testCreateWithoutUuidKey(): void {
    * @covers ::doCreate
    *
    * @return \Drupal\Core\Entity\EntityInterface
+   *   The newly created entity instance with the specified ID and generated UUID.
    */
   public function testCreate() {
     $entity = $this->getMockEntity(EntityBaseTest::class, [], ['toArray']);
@@ -241,6 +242,7 @@ public function testCreate() {
    *   The entity.
    *
    * @return \Drupal\Core\Entity\EntityInterface
+   *   The saved entity instance after insertion.
    *
    * @depends testCreate
    */
@@ -284,6 +286,7 @@ public function testSaveInsert(EntityInterface $entity) {
    *   The entity.
    *
    * @return \Drupal\Core\Entity\EntityInterface
+   *   The updated entity instance after saving.
    *
    * @depends testSaveInsert
    */
@@ -616,6 +619,7 @@ public function testDeleteNothing(): void {
    *   (optional) The methods to mock.
    *
    * @return \Drupal\Core\Entity\EntityInterface&\PHPUnit\Framework\MockObject\MockObject
+   *   A mock entity instance with the specified methods mocked.
    */
   protected function getMockEntity(string $class = EntityBaseTest::class, array $arguments = [], array $methods = []): EntityInterface&MockObject {
     // Ensure the entity is passed at least an array of values and an entity
diff --git a/core/tests/Drupal/Tests/Core/Entity/Routing/DefaultHtmlRouteProviderTest.php b/core/tests/Drupal/Tests/Core/Entity/Routing/DefaultHtmlRouteProviderTest.php
index 82593d4aa6b26a32efba91dfe0347098629e9f8c..23e879bb89f3411c309e408a6a197d17f6402ac9 100644
--- a/core/tests/Drupal/Tests/Core/Entity/Routing/DefaultHtmlRouteProviderTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/Routing/DefaultHtmlRouteProviderTest.php
@@ -383,6 +383,7 @@ public function testGetEntityTypeIdKeyTypeNotFieldable(): void {
    *   (optional) The prophesize base entity type.
    *
    * @return \Prophecy\Prophecy\ObjectProphecy<\Drupal\Core\Entity\EntityTypeInterface>
+   *   The entity type prophecy.
    */
   protected static function getEntityType(?ObjectProphecy $base_entity_type = NULL): ObjectProphecy {
     $entity_type = (new Prophet())->prophesize(EntityTypeInterface::class);
diff --git a/core/tests/Drupal/Tests/Core/Entity/Sql/DefaultTableMappingTest.php b/core/tests/Drupal/Tests/Core/Entity/Sql/DefaultTableMappingTest.php
index 4d468847ac8e0610804d664c1218cbfda46f6a2b..2122d852c83d9fb594d3977d0106f09239b626a3 100644
--- a/core/tests/Drupal/Tests/Core/Entity/Sql/DefaultTableMappingTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/Sql/DefaultTableMappingTest.php
@@ -588,6 +588,7 @@ public static function providerTestGetDedicatedTableName() {
    *   field.
    *
    * @return \Drupal\Core\Field\FieldStorageDefinitionInterface|\PHPUnit\Framework\MockObject\MockObject
+   *   A mock field storage definition with configured field properties.
    */
   protected function setUpDefinition($name, array $column_names, $base_field = TRUE) {
     $definition = $this->createMock('Drupal\Tests\Core\Field\TestBaseFieldDefinitionInterface');
diff --git a/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php b/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
index 7299a0a6cac706b052e6670fc1ec7e2b779a9294..931874ef89080edff2465e7973c6836b3bc9af7e 100644
--- a/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
@@ -678,6 +678,8 @@ public function testChildAccessInheritance($element, $access_checks): void {
    * Data provider for testChildAccessInheritance.
    *
    * @return array
+   *   An array of test cases, each containing a form element structure and
+   *   its expected access results.
    */
   public static function providerTestChildAccessInheritance() {
     $data = [];
@@ -985,6 +987,8 @@ public function testFormTokenCacheability($token, $is_authenticated, $method, $o
    * Data provider for testFormTokenCacheability.
    *
    * @return array
+   *   An array of test cases, each containing a form token, the authentication,
+   *   request method, and expected cacheability outcome.
    */
   public static function providerTestFormTokenCacheability() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Form/FormSubmitterTest.php b/core/tests/Drupal/Tests/Core/Form/FormSubmitterTest.php
index ebeffbc8f17c07ac04f6c0724c02badf8455ad71..38614f06204ef04676c80e29ffa89eac9a011378 100644
--- a/core/tests/Drupal/Tests/Core/Form/FormSubmitterTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/FormSubmitterTest.php
@@ -262,6 +262,7 @@ public function testExecuteSubmitHandlers(): void {
 
   /**
    * @return \Drupal\Core\Form\FormSubmitterInterface
+   *   A mocked instance of FormSubmitter.
    */
   protected function getFormSubmitter() {
     $request_stack = new RequestStack();
diff --git a/core/tests/Drupal/Tests/Core/Form/OptGroupTest.php b/core/tests/Drupal/Tests/Core/Form/OptGroupTest.php
index bdba83a68910160b7017da49749bf3dc24b10cfa..87435ffe903a19ba4e1b53613806e829661ff880 100644
--- a/core/tests/Drupal/Tests/Core/Form/OptGroupTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/OptGroupTest.php
@@ -26,6 +26,7 @@ public function testFlattenOptions($options): void {
    * Provides test data for the flattenOptions() method.
    *
    * @return array
+   *   An array of option structures to be flattened.
    */
   public static function providerTestFlattenOptions() {
     $object1 = new \stdClass();
diff --git a/core/tests/Drupal/Tests/Core/GroupIncludesTestTrait.php b/core/tests/Drupal/Tests/Core/GroupIncludesTestTrait.php
index 8047c1412c13d5b7f24bba6931cb777e1eebfbdd..21157cdf1a0509be18e9aa527558e7652c137b64 100644
--- a/core/tests/Drupal/Tests/Core/GroupIncludesTestTrait.php
+++ b/core/tests/Drupal/Tests/Core/GroupIncludesTestTrait.php
@@ -16,6 +16,7 @@ trait GroupIncludesTestTrait {
 
   /**
    * @return array[]
+   *   An array of module filenames mapped to their virtual file system paths.
    */
   public static function setupGroupIncludes(): array {
     vfsStream::setup('drupal_root');
diff --git a/core/tests/Drupal/Tests/Core/Http/ClientFactoryTest.php b/core/tests/Drupal/Tests/Core/Http/ClientFactoryTest.php
index 527258fc75b162c4a982914385ce1771d96c33f3..329feea31ed1d2a4c6bbdc6cac41291593f16c56 100644
--- a/core/tests/Drupal/Tests/Core/Http/ClientFactoryTest.php
+++ b/core/tests/Drupal/Tests/Core/Http/ClientFactoryTest.php
@@ -63,6 +63,7 @@ public function testCreateFromOptions($settings_config, $parameter_config, $expe
    * Data provider for testCreateFromOptions.
    *
    * @return array
+   *   An array of test data for testCreateFromOptions.
    */
   public static function providerTestCreateFromOptions() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Image/ImageTest.php b/core/tests/Drupal/Tests/Core/Image/ImageTest.php
index 673aeb534eb63b2607572226efc4db3529c3c3d4..dde3e5728cb22fab37ac761491014c54f19eb665 100644
--- a/core/tests/Drupal/Tests/Core/Image/ImageTest.php
+++ b/core/tests/Drupal/Tests/Core/Image/ImageTest.php
@@ -62,6 +62,7 @@ protected function setUp(): void {
    *   (optional) Array containing methods to be replaced with stubs.
    *
    * @return \PHPUnit\Framework\MockObject\MockObject
+   *   Mocked GDToolkit instance.
    */
   protected function getToolkitMock(array $stubs = []) {
     $mock_builder = $this->getMockBuilder('Drupal\system\Plugin\ImageToolkit\GDToolkit');
@@ -81,6 +82,7 @@ protected function getToolkitMock(array $stubs = []) {
    *   The image toolkit object.
    *
    * @return \PHPUnit\Framework\MockObject\MockObject
+   *   Mocked GDToolkit operation instance.
    */
   protected function getToolkitOperationMock($class_name, ImageToolkitInterface $toolkit) {
     $mock_builder = $this->getMockBuilder('Drupal\system\Plugin\ImageToolkit\Operation\gd\\' . $class_name);
diff --git a/core/tests/Drupal/Tests/Core/Menu/LocalTaskManagerTest.php b/core/tests/Drupal/Tests/Core/Menu/LocalTaskManagerTest.php
index 4b9504eb3b355e0f08c39c683effbcf0484fe3b5..6a35e40e1da07d0822e6f42537d5a7266e5ada4f 100644
--- a/core/tests/Drupal/Tests/Core/Menu/LocalTaskManagerTest.php
+++ b/core/tests/Drupal/Tests/Core/Menu/LocalTaskManagerTest.php
@@ -362,6 +362,7 @@ protected function getLocalTasksForRouteResult($mock_plugin): array {
    * Returns the cache entry expected when running getLocalTaskForRoute().
    *
    * @return array
+   *   The expected cache entry.
    */
   protected function getLocalTasksCache(): array {
     $local_task_fixtures = $this->getLocalTaskFixtures();
diff --git a/core/tests/Drupal/Tests/Core/Plugin/LazyPluginCollectionTestBase.php b/core/tests/Drupal/Tests/Core/Plugin/LazyPluginCollectionTestBase.php
index a4f169b1565ff8c7d7436978548e4ef3f5e2f60d..5893381194061f82245ba47d0ec019b8b889860c 100644
--- a/core/tests/Drupal/Tests/Core/Plugin/LazyPluginCollectionTestBase.php
+++ b/core/tests/Drupal/Tests/Core/Plugin/LazyPluginCollectionTestBase.php
@@ -105,6 +105,7 @@ public function returnPluginMap($plugin_id) {
    *   The plugin definition.
    *
    * @return \Drupal\Component\Plugin\PluginInspectionInterface|\PHPUnit\Framework\MockObject\MockObject
+   *   The mocked plugin object.
    */
   protected function getPluginMock($plugin_id, array $definition) {
     // Create a mock plugin instance.
diff --git a/core/tests/Drupal/Tests/Core/Plugin/PluginDependencyTraitTest.php b/core/tests/Drupal/Tests/Core/Plugin/PluginDependencyTraitTest.php
index 41976c89e00ce0d3d93bdf33af81b2b02275eed5..e16672c8dbe345bb06dac7eb99dac9ee852a262c 100644
--- a/core/tests/Drupal/Tests/Core/Plugin/PluginDependencyTraitTest.php
+++ b/core/tests/Drupal/Tests/Core/Plugin/PluginDependencyTraitTest.php
@@ -209,6 +209,7 @@ protected function themeHandler() {
 
   /**
    * @return array[]
+   *   The dependencies.
    */
   public function getDependencies() {
     return $this->dependencies;
diff --git a/core/tests/Drupal/Tests/Core/Plugin/PluginWithFormsTraitTest.php b/core/tests/Drupal/Tests/Core/Plugin/PluginWithFormsTraitTest.php
index 459d26de709a976a6f7c31c0e7616886b7dbba6d..779877a2a4e4e3883dd64790e1f5095cc04aa64a 100644
--- a/core/tests/Drupal/Tests/Core/Plugin/PluginWithFormsTraitTest.php
+++ b/core/tests/Drupal/Tests/Core/Plugin/PluginWithFormsTraitTest.php
@@ -29,6 +29,7 @@ public function testGetFormClass(PluginWithFormsInterface $block_plugin, $operat
 
   /**
    * @return array
+   *   Test cases for different block plugins and operations, mapping them to expected form classes.
    */
   public static function providerGetFormClass() {
     $block_plugin_without_forms = new TestClass([], 'block_plugin_without_forms', [
diff --git a/core/tests/Drupal/Tests/Core/Render/BubbleableMetadataTest.php b/core/tests/Drupal/Tests/Core/Render/BubbleableMetadataTest.php
index 2307b355e7bae69051d3305baa616c83e7d8cac8..9089408e9062f66d6a71827d9de380f717106aea 100644
--- a/core/tests/Drupal/Tests/Core/Render/BubbleableMetadataTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/BubbleableMetadataTest.php
@@ -68,6 +68,7 @@ public function testMerge(BubbleableMetadata $a, CacheableMetadata $b, Bubbleabl
    * Provides test data for testMerge().
    *
    * @return array
+   *   An array of test data for testMerge().
    */
   public static function providerTestMerge() {
     return [
@@ -143,6 +144,7 @@ public function testApplyTo(BubbleableMetadata $metadata, array $render_array, a
    * Provides test data for testApplyTo().
    *
    * @return array
+   *   An array of test data for testApplyTo().
    */
   public static function providerTestApplyTo() {
     $data = [];
@@ -207,6 +209,7 @@ public function testCreateFromRenderArray(array $render_array, BubbleableMetadat
    * Provides test data for createFromRenderArray().
    *
    * @return array
+   *   An array of test data for createFromRenderArray().
    */
   public static function providerTestCreateFromRenderArray() {
     $data = [];
@@ -401,6 +404,7 @@ public function testMergeAttachmentsHtmlHeadMerging($a, $b, $expected): void {
    * Data provider for testMergeAttachmentsHtmlHeadMerging.
    *
    * @return array
+   *   An array of test data for testMergeAttachmentsHtmlHeadMerging.
    */
   public static function providerTestMergeAttachmentsHtmlHeadMerging() {
     $meta = [
@@ -474,6 +478,7 @@ public function testMergeAttachmentsHtmlHeadLinkMerging($a, $b, $expected): void
    * Data provider for testMergeAttachmentsHtmlHeadLinkMerging.
    *
    * @return array
+   *   An array of test data for testMergeAttachmentsHtmlHeadLinkMerging.
    */
   public static function providerTestMergeAttachmentsHtmlHeadLinkMerging() {
     $rel = [
@@ -540,6 +545,7 @@ public function testMergeAttachmentsHttpHeaderMerging($a, $b, $expected): void {
    * Data provider for testMergeAttachmentsHttpHeaderMerging.
    *
    * @return array
+   *   An array of test data for testMergeAttachmentsHttpHeaderMerging.
    */
   public static function providerTestMergeAttachmentsHttpHeaderMerging() {
     $content_type = [
@@ -614,6 +620,7 @@ public function testAddCacheableDependency(BubbleableMetadata $a, $b, Bubbleable
    * Provides test data for testMerge().
    *
    * @return array
+   *   An array of test data for testMerge().
    */
   public function providerTestAddCacheableDependency() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Render/ElementInfoManagerTest.php b/core/tests/Drupal/Tests/Core/Render/ElementInfoManagerTest.php
index a9ede9f13c8e2e373bed67eec9705ac89ec23a37..abd1cc4ead37f43fd354c7ff63e8479e5b7c7c97 100644
--- a/core/tests/Drupal/Tests/Core/Render/ElementInfoManagerTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/ElementInfoManagerTest.php
@@ -113,6 +113,7 @@ public function testGetInfoElementPlugin($plugin_class, $expected_info): void {
    * Provides tests data for testGetInfoElementPlugin().
    *
    * @return array
+   *   An array of test data for testGetInfoElementPlugin().
    */
   public static function providerTestGetInfoElementPlugin() {
     $data = [];
diff --git a/core/tests/Drupal/Tests/Core/Render/ElementTest.php b/core/tests/Drupal/Tests/Core/Render/ElementTest.php
index fd71a85a59dc0f33f3e2912f9356feac6d90712e..e511d6af3f7c6d28a16c57d038ba95b8602cf97b 100644
--- a/core/tests/Drupal/Tests/Core/Render/ElementTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/ElementTest.php
@@ -141,6 +141,7 @@ public function testVisibleChildren(array $element, array $expected_keys): void
    * Data provider for testVisibleChildren.
    *
    * @return array
+   *   An array of test cases.
    */
   public static function providerVisibleChildren() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Render/Placeholder/ChainedPlaceholderStrategyTest.php b/core/tests/Drupal/Tests/Core/Render/Placeholder/ChainedPlaceholderStrategyTest.php
index 34e2f44b88d4dedd67af33dfd8183ccf0cf55e64..f1344b0ce8e2ae7dc2fe3de42d130e23386d9d80 100644
--- a/core/tests/Drupal/Tests/Core/Render/Placeholder/ChainedPlaceholderStrategyTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/Placeholder/ChainedPlaceholderStrategyTest.php
@@ -34,6 +34,7 @@ public function testProcessPlaceholders($strategies, $placeholders, $result): vo
    * Provides a list of render strategies, placeholders and results.
    *
    * @return array
+   *   An array of render strategies, placeholders and results.
    */
   public static function providerProcessPlaceholders() {
     $prophet = new Prophet();
diff --git a/core/tests/Drupal/Tests/Core/Render/PlaceholderGeneratorTest.php b/core/tests/Drupal/Tests/Core/Render/PlaceholderGeneratorTest.php
index 065cdc6d15a2e2e7ee4862cad4949e07462eedbd..21e9e7011d3556a7810d81356ae822ede4d8f2ed 100644
--- a/core/tests/Drupal/Tests/Core/Render/PlaceholderGeneratorTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/PlaceholderGeneratorTest.php
@@ -86,6 +86,7 @@ public function testRenderPlaceholdersDifferentSortedContextsTags(): void {
 
   /**
    * @return array
+   *   An array of test cases with different placeholder inputs.
    */
   public static function providerCreatePlaceholderGeneratesValidHtmlMarkup() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Render/RendererBubblingTest.php b/core/tests/Drupal/Tests/Core/Render/RendererBubblingTest.php
index 52944069309c2050279b68b23d9d73cfc2ebeb6f..2a6f20bb6cd9127b7c5fc25c4cb9a85b243890da 100644
--- a/core/tests/Drupal/Tests/Core/Render/RendererBubblingTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/RendererBubblingTest.php
@@ -500,6 +500,7 @@ public function testBubblingWithPrerender($test_element): void {
    * Provides two test elements: one without, and one with the theme system.
    *
    * @return array
+   *   An array of test cases, each containing a render array with different configurations.
    */
   public static function providerTestBubblingWithPrerender() {
     $data = [];
diff --git a/core/tests/Drupal/Tests/Core/Render/RendererPlaceholdersTest.php b/core/tests/Drupal/Tests/Core/Render/RendererPlaceholdersTest.php
index 3f05b89465ce1a77d2c198ab0158f0328ebbf408..14aafbc8adabd03099f8059f8c1e48d632cbdc3e 100644
--- a/core/tests/Drupal/Tests/Core/Render/RendererPlaceholdersTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/RendererPlaceholdersTest.php
@@ -62,6 +62,7 @@ protected function setUp(): void {
    *   https://www.drupal.org/node/2559847
    *
    * @return array
+   *   An array of test cases.
    */
   public static function providerPlaceholders(): array {
     $args = [static::randomContextValue()];
@@ -1150,6 +1151,7 @@ protected function generatePlaceholdersWithChildrenTestElement(array $args_1, ar
 
   /**
    * @return \Drupal\Core\Theme\ThemeManagerInterface|\PHPUnit\Framework\MockObject\Builder\InvocationMocker
+   *   The mocked theme manager.
    */
   protected function setupThemeManagerForDetails() {
     return $this->themeManager->expects($this->any())
diff --git a/core/tests/Drupal/Tests/Core/Render/RendererTest.php b/core/tests/Drupal/Tests/Core/Render/RendererTest.php
index b08e2910c09264e83a0520f17b3cc4f0245ff3ad..e9a27fd6cd6521d03a90791f9bcdb57f8ba536fb 100644
--- a/core/tests/Drupal/Tests/Core/Render/RendererTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/RendererTest.php
@@ -69,6 +69,7 @@ public function testRenderBasic($build, $expected, ?callable $setup_code = NULL)
    * Provides a list of render arrays to test basic rendering.
    *
    * @return array
+   *   An array of render arrays and their expected output.
    */
   public static function providerTestRenderBasic(): array {
     $data = [];
@@ -672,6 +673,7 @@ public function testRenderTwice($build): void {
    * Provides a list of render array iterations.
    *
    * @return array
+   *   An array of render arrays.
    */
   public static function providerRenderTwice() {
     return [
@@ -726,6 +728,7 @@ public function testRenderChildrenAccess(): void {
    * Provides a list of both booleans.
    *
    * @return array
+   *   A list of boolean values and AccessResult objects.
    */
   public static function providerAccessValues() {
     return [
@@ -801,6 +804,7 @@ public function testRenderWithThemeArguments(): void {
    * Provides a list of access conditions and expected cache metadata.
    *
    * @return array
+   *   An array of access conditions and expected cache metadata.
    */
   public static function providerRenderCache() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/RouteProcessor/RouteProcessorManagerTest.php b/core/tests/Drupal/Tests/Core/RouteProcessor/RouteProcessorManagerTest.php
index 625814a39c9edb84da5996ff0fdd4165feff8128..0f0b4548cef5737497982bb1f827a5f3b7abdc3a 100644
--- a/core/tests/Drupal/Tests/Core/RouteProcessor/RouteProcessorManagerTest.php
+++ b/core/tests/Drupal/Tests/Core/RouteProcessor/RouteProcessorManagerTest.php
@@ -68,6 +68,7 @@ public function testRouteProcessorManager(): void {
    *   The parameters to use in mock with() expectation.
    *
    * @return \Drupal\Core\RouteProcessor\OutboundRouteProcessorInterface|\PHPUnit\Framework\MockObject\MockObject
+   *   The mock processor object.
    */
   protected function getMockProcessor($route_name, $route, $parameters) {
     $processor = $this->createMock('Drupal\Core\RouteProcessor\OutboundRouteProcessorInterface');
diff --git a/core/tests/Drupal/Tests/Core/Routing/RouteMatchTestBase.php b/core/tests/Drupal/Tests/Core/Routing/RouteMatchTestBase.php
index 8fffba927ecb2845d971e1f65ad0400b37aa9d81..abb0bda7994f8928bbacc16049602c095c1ed274 100644
--- a/core/tests/Drupal/Tests/Core/Routing/RouteMatchTestBase.php
+++ b/core/tests/Drupal/Tests/Core/Routing/RouteMatchTestBase.php
@@ -28,6 +28,7 @@ abstract class RouteMatchTestBase extends UnitTestCase {
    *   Raw parameters array
    *
    * @return \Drupal\Core\Routing\RouteMatchInterface
+   *   The constructed route match instance.
    */
   abstract protected static function getRouteMatch(string $name, Route $route, array $parameters, array $raw_parameters): RouteMatchInterface;
 
diff --git a/core/tests/Drupal/Tests/Core/Routing/RoutingFixtures.php b/core/tests/Drupal/Tests/Core/Routing/RoutingFixtures.php
index 990a0addd0ac08260df1ed64387805baf069d9ef..1c5e033f425acac7755ab0a0e92e1502b1a0854f 100644
--- a/core/tests/Drupal/Tests/Core/Routing/RoutingFixtures.php
+++ b/core/tests/Drupal/Tests/Core/Routing/RoutingFixtures.php
@@ -83,6 +83,7 @@ public function staticSampleRouteCollection() {
    * Returns a standard set of routes for testing.
    *
    * @return \Symfony\Component\Routing\RouteCollection
+   *   An array of of predefined routes for testing.
    */
   public function sampleRouteCollection() {
     $collection = new RouteCollection();
@@ -115,6 +116,7 @@ public function sampleRouteCollection() {
    * Returns a complex set of routes for testing.
    *
    * @return \Symfony\Component\Routing\RouteCollection
+   *   A RouteCollection with varied route structures.
    */
   public function complexRouteCollection() {
     $collection = new RouteCollection();
@@ -145,6 +147,7 @@ public function complexRouteCollection() {
    * Returns a complex set of routes for testing.
    *
    * @return \Symfony\Component\Routing\RouteCollection
+   *   A RouteCollection containing routes with mixed casing and Unicode characters.
    */
   public function mixedCaseRouteCollection() {
     $collection = new RouteCollection();
@@ -179,6 +182,7 @@ public function mixedCaseRouteCollection() {
    * Returns a complex set of routes for testing.
    *
    * @return \Symfony\Component\Routing\RouteCollection
+   *   A RouteCollection containing duplicate paths with different route names.
    */
   public function duplicatePathsRouteCollection() {
     $collection = new RouteCollection();
@@ -217,6 +221,7 @@ public function duplicatePathsRouteCollection() {
    * Returns a Content-type restricted set of routes for testing.
    *
    * @return \Symfony\Component\Routing\RouteCollection
+   *   A RouteCollection containing routes with Content-type restrictions for testing.
    */
   public function contentRouteCollection() {
     $collection = new RouteCollection();
diff --git a/core/tests/Drupal/Tests/Core/Routing/TrustedRedirectResponseTest.php b/core/tests/Drupal/Tests/Core/Routing/TrustedRedirectResponseTest.php
index fb6183466a5cba9d4162aabc84babc45a5742995..ef5d674f605d456bd8fbd358a95ed599593567c5 100644
--- a/core/tests/Drupal/Tests/Core/Routing/TrustedRedirectResponseTest.php
+++ b/core/tests/Drupal/Tests/Core/Routing/TrustedRedirectResponseTest.php
@@ -74,6 +74,7 @@ public function testCreateFromRedirectResponse($redirect_response): void {
 
   /**
    * @return array
+   *   An array of test cases, each containing a redirect response instance.
    */
   public static function providerCreateFromRedirectResponse() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php b/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
index 26c3b7663a56807744ffaf0a5a994fbd3985a398..97cb548fa468958b0f455d86c2220f85a8d6fc16 100644
--- a/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
+++ b/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
@@ -186,6 +186,7 @@ protected function setUp(): void {
    * to return an actual alias.
    *
    * @return string
+   *   The alias for the given path, or the path itself if no alias is defined.
    */
   public function aliasManagerCallback() {
     $args = func_get_args();
diff --git a/core/tests/Drupal/Tests/Core/Security/RequestSanitizerTest.php b/core/tests/Drupal/Tests/Core/Security/RequestSanitizerTest.php
index 0ac65036e28c95ad6df9fa497b83ae04a5afd90c..a786ffe8abd946b2df5f12291dc832ce79fbbb7f 100644
--- a/core/tests/Drupal/Tests/Core/Security/RequestSanitizerTest.php
+++ b/core/tests/Drupal/Tests/Core/Security/RequestSanitizerTest.php
@@ -106,6 +106,7 @@ public function testRequestSanitization(Request $request, array $expected = [],
    * Data provider for testRequestSanitization.
    *
    * @return array
+   *   An array of test data for testRequestSanitization.
    */
   public static function providerTestRequestSanitization() {
     $tests = [];
diff --git a/core/tests/Drupal/Tests/Core/Session/AccessPolicyProcessorTest.php b/core/tests/Drupal/Tests/Core/Session/AccessPolicyProcessorTest.php
index 75e0e4f90bf92a10d1947a43b4a2a098b2e56b49..d7fa634a8ac3de49026818dbfcc60554a2211a54 100644
--- a/core/tests/Drupal/Tests/Core/Session/AccessPolicyProcessorTest.php
+++ b/core/tests/Drupal/Tests/Core/Session/AccessPolicyProcessorTest.php
@@ -367,6 +367,7 @@ public function testCacheContextCaching(): void {
    * Sets up the access policy processor.
    *
    * @return \Drupal\Core\Session\AccessPolicyProcessorInterface
+   *   The access policy processor.
    */
   protected function setUpAccessPolicyProcessor(
     ?VariationCacheInterface $variation_cache = NULL,
diff --git a/core/tests/Drupal/Tests/Core/Session/SessionConfigurationTest.php b/core/tests/Drupal/Tests/Core/Session/SessionConfigurationTest.php
index a68788cc47738401090fe3211e93d4fbcf5221e8..b0460940a057893b887dcb95290605020482dce2 100644
--- a/core/tests/Drupal/Tests/Core/Session/SessionConfigurationTest.php
+++ b/core/tests/Drupal/Tests/Core/Session/SessionConfigurationTest.php
@@ -17,6 +17,7 @@ class SessionConfigurationTest extends UnitTestCase {
    * Constructs a partially mocked SUT.
    *
    * @return \Drupal\Core\Session\SessionConfiguration|\PHPUnit\Framework\MockObject\MockObject
+   *   A mock object of SessionConfiguration with specific methods overridden.
    */
   protected function createSessionConfiguration($options = []) {
     return $this->getMockBuilder('Drupal\Core\Session\SessionConfiguration')
diff --git a/core/tests/Drupal/Tests/Core/Site/SettingsTest.php b/core/tests/Drupal/Tests/Core/Site/SettingsTest.php
index 68c9e56f7c9db1e24286f0d7b26f7880417d319e..b57d4ac16c8a7f2bcdadbb5c1f6b8b2fe0ea0d7d 100644
--- a/core/tests/Drupal/Tests/Core/Site/SettingsTest.php
+++ b/core/tests/Drupal/Tests/Core/Site/SettingsTest.php
@@ -100,6 +100,7 @@ public function testGetHashSaltEmpty(array $config): void {
    * Data provider for testGetHashSaltEmpty.
    *
    * @return array
+   *   An array of settings arrays with no hash salt value.
    */
   public static function providerTestGetHashSaltEmpty() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/StringTranslation/TranslationManagerTest.php b/core/tests/Drupal/Tests/Core/StringTranslation/TranslationManagerTest.php
index 51b3082d944f91ae1e69d2cfb81d0889d3688313..774d183acd53adea26328639b5eb54f6b4155e3a 100644
--- a/core/tests/Drupal/Tests/Core/StringTranslation/TranslationManagerTest.php
+++ b/core/tests/Drupal/Tests/Core/StringTranslation/TranslationManagerTest.php
@@ -34,6 +34,7 @@ protected function setUp(): void {
    * Provides some test data for formatPlural()
    *
    * @return array
+   *   An array of test data for formatPlural().
    */
   public static function providerTestFormatPlural() {
     return [
@@ -88,6 +89,7 @@ public function testTranslatePlaceholder($string, array $args, $expected_string)
    * Provides test data for translate().
    *
    * @return array
+   *   An array of test data for translate().
    */
   public static function providerTestTranslatePlaceholder() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php b/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php
index 158c8749239cc2371d1d4d8e40252f5178e4c5e9..8862dc563d4837969487b21aeae3f455dc3d73c4 100644
--- a/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php
+++ b/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php
@@ -448,6 +448,7 @@ public function testTwigAddSuggestionFilter($original_render_array, $suggestion,
    * Provides data for ::testTwigAddSuggestionFilter().
    *
    * @return \Iterator
+   *   An iterator of test data.
    */
   public static function providerTestTwigAddSuggestionFilter(): \Iterator {
     yield 'suggestion should be added' => [
@@ -564,6 +565,7 @@ public function testTwigAddClass($element, $classes, $expected_result): void {
    * Provides data for ::testTwigAddClass().
    *
    * @return \Iterator
+   *   An iterator of test data for ::testTwigAddClass().
    */
   public static function providerTestTwigAddClass(): \Iterator {
     yield 'should add a class on element' => [
@@ -614,6 +616,7 @@ public function testTwigSetAttribute($element, $key, $value, $expected_result):
    * A data provider for ::testTwigSetAttribute().
    *
    * @return \Iterator
+   *   An iterator of test data for ::testTwigSetAttribute().
    */
   public static function providerTestTwigSetAttribute(): \Iterator {
     yield 'should add attributes on element' => [
diff --git a/core/tests/Drupal/Tests/Core/Template/TwigSandboxTest.php b/core/tests/Drupal/Tests/Core/Template/TwigSandboxTest.php
index 4fdeae02e12b192b0220954258384693f0e63c76..ab15d8a2b17f34f2ba0948b5cbddb8ea244cce02 100644
--- a/core/tests/Drupal/Tests/Core/Template/TwigSandboxTest.php
+++ b/core/tests/Drupal/Tests/Core/Template/TwigSandboxTest.php
@@ -57,6 +57,7 @@ public function testEntityDangerousMethods($template): void {
    * Data provider for ::testEntityDangerousMethods.
    *
    * @return array
+   *   An array of dangerous methods.
    */
   public static function getTwigEntityDangerousMethods() {
     return [
diff --git a/core/tests/Drupal/Tests/Core/Test/WebDriverTestBaseTest.php b/core/tests/Drupal/Tests/Core/Test/WebDriverTestBaseTest.php
index f7e417875e1856262a1dcfdfd64a2b419b20b285..68b53ebd82fd7603127d4d872061b915d5b4c56e 100644
--- a/core/tests/Drupal/Tests/Core/Test/WebDriverTestBaseTest.php
+++ b/core/tests/Drupal/Tests/Core/Test/WebDriverTestBaseTest.php
@@ -47,6 +47,7 @@ public function testCapabilities($expected, ?string $mink_driver_args_webdriver,
    *   environment variable will be unset.
    *
    * @return void
+   *   No return value.
    */
   private function putEnv(string $variable, ?string $value): void {
     if (is_string($value)) {
diff --git a/core/tests/Drupal/Tests/Core/Theme/ThemeNegotiatorTest.php b/core/tests/Drupal/Tests/Core/Theme/ThemeNegotiatorTest.php
index 62ebf8d1ccbeda78983d3cd9c2ca69f2e467f895..a64de47cf1f590869fbc0ee5ea5f9e63194b8956 100644
--- a/core/tests/Drupal/Tests/Core/Theme/ThemeNegotiatorTest.php
+++ b/core/tests/Drupal/Tests/Core/Theme/ThemeNegotiatorTest.php
@@ -218,6 +218,7 @@ public function testDetermineActiveThemeWithNotApplyingNegotiator(): void {
    *   An array of negotiator IDs.
    *
    * @return \Drupal\Core\Theme\ThemeNegotiator
+   *   The theme negotiator.
    */
   protected function createThemeNegotiator(array $negotiators) {
     $resolver = new ClassResolver($this->container);
diff --git a/core/tests/Drupal/Tests/Core/Transliteration/PhpTransliterationTest.php b/core/tests/Drupal/Tests/Core/Transliteration/PhpTransliterationTest.php
index 088e70325f4713de4a837cce323c4247dd347e65..3d2b2ae641ab9b522b1dec7bc31e7c3f27150e52 100644
--- a/core/tests/Drupal/Tests/Core/Transliteration/PhpTransliterationTest.php
+++ b/core/tests/Drupal/Tests/Core/Transliteration/PhpTransliterationTest.php
@@ -62,6 +62,7 @@ public function testPhpTransliterationWithAlter($langcode, $original, $expected,
    * Provides test data for testPhpTransliterationWithAlter.
    *
    * @return array
+   *   An array of test data for testPhpTransliterationWithAlter.
    */
   public static function providerTestPhpTransliterationWithAlter() {
     $random_generator = new Random();
diff --git a/core/tests/Drupal/Tests/Core/TypedData/RecursiveContextualValidatorTest.php b/core/tests/Drupal/Tests/Core/TypedData/RecursiveContextualValidatorTest.php
index f43d9bcd7dca3cb249b29f363cdb90f1bcf54bd3..105907b29c67a5870e6c6b0905008a9487a3bddd 100644
--- a/core/tests/Drupal/Tests/Core/TypedData/RecursiveContextualValidatorTest.php
+++ b/core/tests/Drupal/Tests/Core/TypedData/RecursiveContextualValidatorTest.php
@@ -190,6 +190,7 @@ public function testPropertiesValidateWithMultipleLevels(): void {
    *   The name to use for the object.
    *
    * @return \Drupal\Core\TypedData\TypedDataInterface|\PHPUnit\Framework\MockObject\MockObject
+   *   The typed data object.
    */
   protected function setupTypedData(array $tree, $name = '') {
     $callback = function ($value, ExecutionContextInterface $context) {
@@ -310,6 +311,7 @@ public function testValidatePropertyValue(): void {
    * Builds some example type data object.
    *
    * @return \Drupal\Core\TypedData\TypedDataInterface|\PHPUnit\Framework\MockObject\MockObject
+   *   A typed data object with nested properties for testing purposes.
    */
   protected function buildExampleTypedDataWithProperties($subkey_value = NULL) {
     $subkey_value = $subkey_value ?: ['subkey1' => 'subvalue1', 'subkey2' => 'subvalue2'];
diff --git a/core/tests/Drupal/Tests/Core/UrlTest.php b/core/tests/Drupal/Tests/Core/UrlTest.php
index 09e54efb1c180d2fa2bed8bee5ce1badac1a5812..84977e722c7f6d218c4be77b1d84d706dd6f75a4 100644
--- a/core/tests/Drupal/Tests/Core/UrlTest.php
+++ b/core/tests/Drupal/Tests/Core/UrlTest.php
@@ -799,6 +799,7 @@ public function testFromRouteUriWithMissingRouteName(): void {
    *   The account to test.
    *
    * @return \Drupal\Core\Access\AccessManagerInterface|\PHPUnit\Framework\MockObject\MockObject
+   *   The mocked access manager.
    */
   protected function getMockAccessManager($access, $account = NULL) {
     $access_manager = $this->createMock('Drupal\Core\Access\AccessManagerInterface');
diff --git a/core/tests/Drupal/Tests/Core/Utility/ErrorTest.php b/core/tests/Drupal/Tests/Core/Utility/ErrorTest.php
index 9d6c740675b401e9b2323e19145b5975c0585de5..2a85573fefd1ebf44fc210ebcf70680c2439e5a0 100644
--- a/core/tests/Drupal/Tests/Core/Utility/ErrorTest.php
+++ b/core/tests/Drupal/Tests/Core/Utility/ErrorTest.php
@@ -80,6 +80,7 @@ public function testFormatBacktrace(array $backtrace, string $expected): void {
    * Data provider for testFormatBacktrace.
    *
    * @return array
+   *   An array of test cases, each containing a backtrace array and its expected formatted string.
    */
   public static function providerTestFormatBacktrace(): array {
     $data = [];
diff --git a/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php b/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php
index b8ba4752fb4d90044399a6d135b9aa58ec13233f..3867617e45d00898bf86622b2a88347c12d7db21 100644
--- a/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php
+++ b/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php
@@ -121,6 +121,7 @@ public function testAssembleWithLocalUri($uri, array $options, $subdir, $expecte
 
   /**
    * @return array
+   *   An array of test data for testAssembleWithLocalUri.
    */
   public static function providerTestAssembleWithLocalUri() {
     return [
diff --git a/core/tests/Drupal/Tests/EntityViewTrait.php b/core/tests/Drupal/Tests/EntityViewTrait.php
index a1568119f8b61b9f71d143c7761fd5a42a16994f..b4952249db89319bc52a3f1b302e3978d44fd317 100644
--- a/core/tests/Drupal/Tests/EntityViewTrait.php
+++ b/core/tests/Drupal/Tests/EntityViewTrait.php
@@ -32,6 +32,7 @@ trait EntityViewTrait {
    *   the current content language.
    *
    * @return array
+   *   The fully built render array of the entity.
    *
    * @see \Drupal\Core\Render\RendererInterface::render()
    */
diff --git a/core/tests/Drupal/Tests/PerformanceData.php b/core/tests/Drupal/Tests/PerformanceData.php
index dad60e1be3529e3d9064ae5999e7bec5f3bc5051..17e01d1c1265a57dd140b4b2bc8b0b1ad6f3433b 100644
--- a/core/tests/Drupal/Tests/PerformanceData.php
+++ b/core/tests/Drupal/Tests/PerformanceData.php
@@ -230,6 +230,7 @@ public function getCacheGetCount(): int {
    *   List of cids keyed by operation and bin.
    *
    * @return void
+   *   No return value.
    */
   public function setCacheOperations(array $cacheOperations): void {
     $this->cacheOperations = $cacheOperations;
diff --git a/core/tests/Drupal/Tests/PerformanceTestTrait.php b/core/tests/Drupal/Tests/PerformanceTestTrait.php
index 914144dd537185aa7365128da7285d51727b0c19..8eff364de15be33fbd56ed459f683cefa6fc9af9 100644
--- a/core/tests/Drupal/Tests/PerformanceTestTrait.php
+++ b/core/tests/Drupal/Tests/PerformanceTestTrait.php
@@ -612,6 +612,7 @@ private function openTelemetryTracing(array $messages, string $service_name): vo
    *   The message to display.
    *
    * @return void
+   *   No return value.
    *
    * @throws \PHPUnit\Framework\ExpectationFailedException
    */
@@ -653,6 +654,7 @@ protected static function isDatabaseCache(DatabaseEvent $event): bool {
    *   An instance of the performance data value object.
    *
    * @return void
+   *   No return value.
    */
   protected function assertMetrics(
     array $expected,
diff --git a/core/tests/Drupal/Tests/TestFileCreationTrait.php b/core/tests/Drupal/Tests/TestFileCreationTrait.php
index 43357296dedeadaaf5879032d7698ed1988843d5..9030ff7c23bff3d0a292bcc75a6b0412013e3b6b 100644
--- a/core/tests/Drupal/Tests/TestFileCreationTrait.php
+++ b/core/tests/Drupal/Tests/TestFileCreationTrait.php
@@ -112,6 +112,7 @@ protected function getTestFiles($type, $size = NULL) {
    *   The second class.
    *
    * @return int
+   *   -1 if $file1 is smaller than $file2, 0 if they are the same size, and 1
    */
   protected function compareFiles($file1, $file2): int {
     $compare_size = filesize($file1->uri) - filesize($file2->uri);
diff --git a/core/tests/Drupal/Tests/TestRequirementsTrait.php b/core/tests/Drupal/Tests/TestRequirementsTrait.php
index 04c2eb411dba71566b6256003c7bd3f92ade8100..579419da58e527590a0fc53f7922a3d563d4c8d7 100644
--- a/core/tests/Drupal/Tests/TestRequirementsTrait.php
+++ b/core/tests/Drupal/Tests/TestRequirementsTrait.php
@@ -17,6 +17,7 @@ trait TestRequirementsTrait {
    * Returns the Drupal root directory.
    *
    * @return string
+   *   The Drupal root directory.
    */
   protected static function getDrupalRoot(): string {
     return dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__)), 2);
diff --git a/core/tests/Drupal/Tests/WebAssert.php b/core/tests/Drupal/Tests/WebAssert.php
index 248da850b7cb441f2f9372c5514aba879219d5ce..79195aab829eb86496b921d80cdecae269904568 100644
--- a/core/tests/Drupal/Tests/WebAssert.php
+++ b/core/tests/Drupal/Tests/WebAssert.php
@@ -53,6 +53,7 @@ public function __construct(Session $session, $base_url = '') {
    *   Whether to include the query string in the return value.
    *
    * @return string
+   *   The cleaned URL with the base URL removed and formatted consistently.
    */
   protected function cleanUrl(string|Url $url, bool $include_query = FALSE) {
     if ($url instanceof Url) {
@@ -769,6 +770,7 @@ public function pageContainsNoDuplicateId() {
    *   A url string, or object.
    *
    * @return void
+   *   No return value.
    *
    * @throws \Behat\Mink\Exception\ExpectationException
    */