diff --git a/core/lib/Drupal/Core/Config/ConfigManager.php b/core/lib/Drupal/Core/Config/ConfigManager.php
index fb8f658..eb59497 100644
--- a/core/lib/Drupal/Core/Config/ConfigManager.php
+++ b/core/lib/Drupal/Core/Config/ConfigManager.php
@@ -155,11 +155,15 @@ public function diff(StorageInterface $source_storage, StorageInterface $target_
     // Check for new or removed files.
     if ($source_data === array('false')) {
       // Added file.
-      $source_data = array($this->t('File added'));
+      // Cast the result of t() to a string, as the diff engine doesn't know
+      // about objects.
+      $source_data = array((string) $this->t('File added'));
     }
     if ($target_data === array('false')) {
       // Deleted file.
-      $target_data = array($this->t('File removed'));
+      // Cast the result of t() to a string, as the diff engine doesn't know
+      // about objects.
+      $target_data = array((string) $this->t('File removed'));
     }
 
     return new Diff($source_data, $target_data);
diff --git a/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
index 6f11827..1b93148 100755
--- a/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -589,6 +589,12 @@ function simpletest_script_execute_batch($test_classes) {
  * Run a group of phpunit tests.
  */
 function simpletest_script_run_phpunit($test_id, $class) {
+
+  $reflection = new \ReflectionClass($class);
+  if ($reflection->hasProperty('runLimit')) {
+    set_time_limit($reflection->getStaticPropertyValue('runLimit'));
+  }
+
   $results = simpletest_run_phpunit_tests($test_id, array($class));
   simpletest_process_phpunit_results($results);
 
diff --git a/core/tests/Drupal/KernelTests/Config/DefaultConfigTest.php b/core/tests/Drupal/KernelTests/Config/DefaultConfigTest.php
index 8efed71..5ac0cb6 100644
--- a/core/tests/Drupal/KernelTests/Config/DefaultConfigTest.php
+++ b/core/tests/Drupal/KernelTests/Config/DefaultConfigTest.php
@@ -27,12 +27,12 @@ class DefaultConfigTest extends KernelTestBase {
   /**
    * {@inheritdoc}
    */
-  public static $modules = ['system', 'user'];
+  protected static $timeLimit = 500;
 
   /**
-   * Time limit for the test.
+   * {@inheritdoc}
    */
-  protected $timeLimit = 120;
+  public static $modules = ['system', 'user'];
 
   /**
    * {@inheritdoc}
@@ -62,10 +62,6 @@ protected function setUp() {
    * @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 */