diff --git a/core/modules/system/src/Tests/Installer/ConfigAfterInstallerTestBase.php b/core/modules/system/src/Tests/Installer/ConfigAfterInstallerTestBase.php
index aa3ec3e..7531424 100644
--- a/core/modules/system/src/Tests/Installer/ConfigAfterInstallerTestBase.php
+++ b/core/modules/system/src/Tests/Installer/ConfigAfterInstallerTestBase.php
@@ -14,7 +14,7 @@
 use Drupal\simpletest\InstallerTestBase;
 
 /**
- * Provides a class for install profiles to check its installed config.
+ * Provides a class for install profiles to check their installed config.
  */
 abstract class ConfigAfterInstallerTestBase extends InstallerTestBase {
 
diff --git a/core/tests/Drupal/KernelTests/AssertConfigTrait.php b/core/tests/Drupal/KernelTests/AssertConfigTrait.php
index 437cf99..24d393e 100644
--- a/core/tests/Drupal/KernelTests/AssertConfigTrait.php
+++ b/core/tests/Drupal/KernelTests/AssertConfigTrait.php
@@ -23,7 +23,7 @@
    *   The config name to check.
    * @param array $skipped_config
    *   An array of skipped config, keyed by string. If the value is TRUE, the
-   *   entire file will be ignored, otherwise its an array of strings which are
+   *   entire file will be ignored, otherwise it's an array of strings which are
    *   ignored.
    *
    * @throws \Exception
diff --git a/core/tests/Drupal/KernelTests/Config/DefaultConfigTest.php b/core/tests/Drupal/KernelTests/Config/DefaultConfigTest.php
index 0ee34e1..8efed71 100644
--- a/core/tests/Drupal/KernelTests/Config/DefaultConfigTest.php
+++ b/core/tests/Drupal/KernelTests/Config/DefaultConfigTest.php
@@ -7,7 +7,6 @@
 
 namespace Drupal\KernelTests\Config;
 
-use Drupal\Component\Diff\Diff;
 use Drupal\Component\FileCache\FileCacheFactory;
 use Drupal\Core\Config\FileStorage;
 use Drupal\Core\Config\InstallStorage;
@@ -15,7 +14,6 @@
 use Drupal\Core\Site\Settings;
 use Drupal\KernelTests\AssertConfigTrait;
 use Drupal\KernelTests\KernelTestBase;
-use Drupal\user\Entity\User;
 
 /**
  * Tests that the installed config matches the default config.
@@ -32,11 +30,16 @@ class DefaultConfigTest extends KernelTestBase {
   public static $modules = ['system', 'user'];
 
   /**
+   * Time limit for the test.
+   */
+  protected $timeLimit = 120;
+
+  /**
    * {@inheritdoc}
    */
   protected function setUp() {
     // @todo Extra hack to avoid test fails, remove this once
-    // https://www.drupal.org/node/2553661 is fixed.
+    //   https://www.drupal.org/node/2553661 is fixed.
     FileCacheFactory::setPrefix(Settings::getApcuPrefix('file_cache', $this->root));
 
     parent::setUp();
@@ -54,9 +57,15 @@ protected function setUp() {
   }
 
   /**
+   * Tests if installed config is equal to the exported config.
+   *
    * @dataProvider providerTestModuleConfig
    */
   public function testModuleConfig($module) {
+    // We're testing a lot of modules. Allow sufficient time for the test to
+    // run.
+    drupal_set_time_limit($this->timeLimit);
+
     /** @var \Drupal\Core\Extension\ModuleInstallerInterface $module_installer */
     $module_installer = $this->container->get('module_installer');
     /** @var \Drupal\Core\Config\StorageInterface $active_config_storage */
@@ -94,6 +103,12 @@ public function testModuleConfig($module) {
     }
   }
 
+  /**
+   * Test data provider for ::testModuleConfig().
+   *
+   * @return array
+   *   An array of module names to test.
+   */
   public function providerTestModuleConfig() {
     $module_dirs = array_keys(iterator_to_array(new \FilesystemIterator(__DIR__ . '/../../../../modules/')));
     $module_names = array_map(function($path) {