diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 1568f45..05afefd 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -10,6 +10,7 @@
 use Drupal\Core\DrupalKernel;
 use Drupal\Core\Database\Database;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
+use Drupal\Core\Config\GlobalConfig;
 use Drupal\Core\Utility\Title;
 use Symfony\Component\ClassLoader\ApcClassLoader;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -567,15 +568,22 @@ function drupal_settings_initialize() {
   // Export these settings.php variables to the global namespace.
   global $databases, $cookie_domain, $conf, $db_prefix, $drupal_hash_salt, $base_secure_url, $base_insecure_url, $config_directories;
   $conf = array();
+  $settings = array();
+  $config = array();
 
   // Make conf_path() available as local variable in settings.php.
   $conf_path = conf_path();
   if (is_readable(DRUPAL_ROOT . '/' . $conf_path . '/settings.php')) {
     include_once DRUPAL_ROOT . '/' . $conf_path . '/settings.php';
   }
-  require_once __DIR__ . '../../lib/Drupal/Component/Utility/Settings.php';
+  // Initialize Settings.
+  require_once __DIR__ . '/../lib/Drupal/Component/Utility/Settings.php';
+  new Settings($settings);
+
+  // Initialize global Config overrides.
+  require_once __DIR__ . '/../lib/Drupal/Core/Config/GlobalConfig.php';
+  GlobalConfig::getInstance()->setConfig($config);
 
-  new Settings(isset($settings) ? $settings : array());
   $is_https = isset($_SERVER['HTTPS']) && strtolower($_SERVER['HTTPS']) == 'on';
 
   if (isset($base_url)) {
@@ -2251,8 +2259,8 @@ function drupal_valid_test_ua($new_prefix = NULL) {
  * Very strictly for internal use only.
  *
  * Loads settings.php from the simpletest public files directory. These files
- * can change the global $conf, the global $config_directories, the return
- * value of conf_path(), and settings().
+ * can change the global $config_directories, the return value of conf_path(),
+ * settings(), and $config overrides.
  *
  * @param string $test_prefix
  *   The simpletest prefix.
@@ -2272,13 +2280,16 @@ function _drupal_load_test_overrides($test_prefix) {
   $filename = conf_path() . '/files/' . $path_prefix . '/settings.php';
   if (file_exists($filename)) {
     $settings = settings()->getAll();
+    $config = GlobalConfig::getInstance()->getAll();
     $conf_path = &drupal_static('conf_path');
-    // This can override $conf, $conf_path, $settings, and $config_directories.
+    // This can override $config, $conf_path, $settings, and $config_directories.
     include $filename;
     // Keep the overriden $conf_path alive across drupal_static_reset() calls.
     // @see conf_path()
     $settings['simpletest_conf_path'] = $conf_path;
     new Settings($settings);
+    // Apply $config overrides.
+    GlobalConfig::getInstance()->setConfig($config);
   }
 }
 
diff --git a/core/lib/Drupal/Core/Config/GlobalConfig.php b/core/lib/Drupal/Core/Config/GlobalConfig.php
new file mode 100644
index 0000000..9d29ed6
--- /dev/null
+++ b/core/lib/Drupal/Core/Config/GlobalConfig.php
@@ -0,0 +1,159 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Config\GlobalConfig.
+ */
+
+namespace Drupal\Core\Config;
+
+/**
+ * Global configuration value overrides.
+ *
+ * Values can be set through the $config variable in settings.php and requested
+ * via GlobalConfig::getInstance()->get($config_name).
+ *
+ * A singleton is used because this class is used before the container (and the
+ * class loader) is available. Additionally, the global override configuration
+ * cannot be altered at runtime; except within a test environment.
+ *
+ * @see drupal_settings_initialize()
+ */
+final class GlobalConfig {
+
+  /**
+   * Array holding the overridden configuration values, keyed by config name.
+   *
+   * @var array
+   */
+  private $storage;
+
+  /**
+   * Singleton instance.
+   *
+   * @var \Drupal\Core\Config\GlobalConfig
+   */
+  private static $instance;
+
+  /**
+   * Returns the settings instance.
+   *
+   * @return \Drupal\Core\Config\GlobalConfig
+   */
+  public static function getInstance() {
+    if (!isset(self::$instance)) {
+      self::$instance = new self();
+    }
+    return self::$instance;
+  }
+
+  /**
+   * Constructor.
+   */
+  private function __construct() {
+    self::$instance = $this;
+  }
+
+  /**
+   * Sets the global override configuration values.
+   *
+   * @param array $config
+   *   An associative array containing all configuration values to override,
+   *   keyed by configuration object name.
+   */
+  public function setConfig(array $config) {
+    if (isset($this->storage) && !drupal_valid_test_ua()) {
+      throw new \BadMethodCallException('GlobalConfig is read-only.');
+    }
+    $this->storage = $config;
+  }
+
+  /**
+   * Overrides a value for a configuration object. Available for tests only.
+   *
+   * @param string $config_name
+   *   The configuration object name for which to set a value.
+   * @param string $keys
+   *   The key within the configuration object to set; sub-keys delimited by
+   *   dots.
+   * @param mixed $value
+   *   The value to set.
+   */
+  public function set($config_name, $keys, $value) {
+    if (!isset($this->storage) || !drupal_valid_test_ua()) {
+      throw new \BadMethodCallException('GlobalConfig is read-only.');
+    }
+    // Inlined NestedArray::setValue(), because this class is used before the
+    // class loader is available.
+    $ref = &$this->storage;
+    foreach (array_merge(array($config_name), explode('.', $keys)) as $key) {
+      $ref = &$ref[$key];
+    }
+    $ref = $value;
+  }
+
+  /**
+   * Overrides a value for a configuration object. Available for tests only.
+   *
+   * @param string $config_name
+   *   The configuration object name for which to set a value.
+   * @param string $keys
+   *   The key within the configuration object to set; sub-keys delimited by
+   *   dots.
+   * @param mixed $value
+   *   The value to set.
+   */
+  public function del($config_name, $keys = NULL) {
+    if (!isset($this->storage) || !drupal_valid_test_ua()) {
+      throw new \BadMethodCallException('GlobalConfig is read-only.');
+    }
+    if (!isset($keys)) {
+      unset($this->storage[$config_name]);
+    }
+    else {
+      // Inlined NestedArray::unsetValue(), because this class is used before
+      // the class loader is available.
+      $parents = array_merge(array($config_name), explode('.', $keys));
+      $unset_key = array_pop($parents);
+      $ref = &$this->storage;
+      foreach ($parents as $key) {
+        $ref = &$ref[$key];
+      }
+      unset($ref[$unset_key]);
+    }
+  }
+
+  /**
+   * Returns whether overridden values exist for a given configuration object name.
+   *
+   * @return bool
+   */
+  public function has($config_name) {
+    return isset($this->storage[$config_name]);
+  }
+
+  /**
+   * Returns override values for a configuration object name, if any.
+   *
+   * @param string $name
+   *   The name of the setting to return.
+   *
+   * @return mixed|null
+   *   The overriden values for the configuration object or NULL if none.
+   */
+  public function get($config_name) {
+    if ($this->has($config_name)) {
+      return $this->storage[$config_name];
+    }
+  }
+
+  /**
+   * Returns all configuration override values.
+   *
+   * @return array
+   */
+  public function getAll() {
+    return $this->storage;
+  }
+
+}
diff --git a/core/lib/Drupal/Core/EventSubscriber/ConfigGlobalOverrideSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/ConfigGlobalOverrideSubscriber.php
index 02bf2cb..462d37a 100644
--- a/core/lib/Drupal/Core/EventSubscriber/ConfigGlobalOverrideSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/ConfigGlobalOverrideSubscriber.php
@@ -9,6 +9,7 @@
 
 use Drupal\Core\Config\Config;
 use Drupal\Core\Config\ConfigEvent;
+use Drupal\Core\Config\GlobalConfig;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 
 /**
@@ -17,24 +18,24 @@
 class ConfigGlobalOverrideSubscriber implements EventSubscriberInterface {
 
   /**
-   * Overrides configuration values with values in global $conf variable.
+   * Overrides configuration values with values from settings.php.
    *
    * @param \Drupal\Core\Config\ConfigEvent $event
    *   The Event to process.
    */
   public function configInit(ConfigEvent $event) {
-    global $conf;
-
     $config = $event->getConfig();
-    if (isset($conf[$config->getName()])) {
-      $config->setOverride($conf[$config->getName()]);
+    $name = $config->getName();
+    $global_config = GlobalConfig::getInstance();
+    if ($global_config->has($name)) {
+      $config->setOverride($global_config->get($name));
     }
   }
 
   /**
    * Implements EventSubscriberInterface::getSubscribedEvents().
    */
-  static function getSubscribedEvents() {
+  public static function getSubscribedEvents() {
     $events['config.init'][] = array('configInit', 30);
     return $events;
   }
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigLocaleOverride.php b/core/modules/config/lib/Drupal/config/Tests/ConfigLocaleOverride.php
index 24edb76..f2673c8 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigLocaleOverride.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigLocaleOverride.php
@@ -223,13 +223,12 @@ function testConfigLocaleLanguageOverride() {
    * Tests locale override in combination with global overrides.
    */
   function testConfigLocaleUserAndGlobalOverride() {
-    global $conf;
-
     // Globally override value for the keys in config_test.system. Although we
     // override the foo key, there are also language overrides, which trump
     // global overrides so the 'foo' key override will never surface.
-    $conf['config_test.system']['foo'] = 'global bar';
-    $conf['config_test.system']['404'] = 'global herp';
+    $config['config_test.system']['foo'] = 'global bar';
+    $config['config_test.system']['404'] = 'global herp';
+    $this->globalConfig->setConfig($config);
 
     $this->installSchema('system', 'variable');
     $this->installConfig(array('language'));
@@ -251,7 +250,7 @@ function testConfigLocaleUserAndGlobalOverride() {
     $user_config_context->setAccount($account);
     $config = \Drupal::config('config_test.system');
     $this->assertIdentical($config->get('foo'), 'fr bar');
-    // Ensure the value overriden from global $conf works.
+    // Ensure the value overriden from global $config works.
     $this->assertIdentical($config->get('404'), 'global herp');
 
     // Ensure that we get the expected value when we leave the user context. The
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigOverrideTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigOverrideTest.php
index a6016c3..311bb84 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigOverrideTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigOverrideTest.php
@@ -10,7 +10,7 @@
 use Drupal\simpletest\DrupalUnitTestBase;
 
 /**
- * Tests configuration overrides via $conf in settings.php.
+ * Tests configuration overrides via $config in settings.php.
  */
 class ConfigOverrideTest extends DrupalUnitTestBase {
 
@@ -24,7 +24,7 @@ class ConfigOverrideTest extends DrupalUnitTestBase {
   public static function getInfo() {
     return array(
       'name' => 'Configuration overrides',
-      'description' => 'Tests configuration overrides via $conf in settings.php.',
+      'description' => 'Tests configuration overrides via $config in settings.php.',
       'group' => 'Configuration',
     );
   }
@@ -38,7 +38,6 @@ public function setUp() {
    * Tests configuration override.
    */
   function testConfOverride() {
-    global $conf;
     $expected_original_data = array(
       'foo' => 'bar',
       'baz' => NULL,
@@ -47,9 +46,10 @@ function testConfOverride() {
 
     // Set globals before installing to prove that the installed file does not
     // contain these values.
-    $conf['config_test.system']['foo'] = 'overridden';
-    $conf['config_test.system']['baz'] = 'injected';
-    $conf['config_test.system']['404'] = 'derp';
+    $overrides['config_test.system']['foo'] = 'overridden';
+    $overrides['config_test.system']['baz'] = 'injected';
+    $overrides['config_test.system']['404'] = 'derp';
+    $this->globalConfig->setConfig($overrides);
 
     config_install_default_config('module', 'config_test');
 
@@ -73,10 +73,10 @@ function testConfOverride() {
     // default).
     $config = \Drupal::config('config_test.system');
 
-    // Verify that it contains the overridden data from $conf.
-    $this->assertIdentical($config->get('foo'), $conf['config_test.system']['foo']);
-    $this->assertIdentical($config->get('baz'), $conf['config_test.system']['baz']);
-    $this->assertIdentical($config->get('404'), $conf['config_test.system']['404']);
+    // Verify that it contains the overridden data from $config.
+    $this->assertIdentical($config->get('foo'), $overrides['config_test.system']['foo']);
+    $this->assertIdentical($config->get('baz'), $overrides['config_test.system']['baz']);
+    $this->assertIdentical($config->get('404'), $overrides['config_test.system']['404']);
 
     // Set the value for 'baz' (on the original data).
     $expected_original_data['baz'] = 'original baz';
@@ -86,19 +86,19 @@ function testConfOverride() {
     $expected_original_data['404'] = 'original 404';
     $config->set('404', $expected_original_data['404']);
 
-    // Verify that it still contains the overridden data from $conf.
-    $this->assertIdentical($config->get('foo'), $conf['config_test.system']['foo']);
-    $this->assertIdentical($config->get('baz'), $conf['config_test.system']['baz']);
-    $this->assertIdentical($config->get('404'), $conf['config_test.system']['404']);
+    // Verify that it still contains the overridden data from $config.
+    $this->assertIdentical($config->get('foo'), $overrides['config_test.system']['foo']);
+    $this->assertIdentical($config->get('baz'), $overrides['config_test.system']['baz']);
+    $this->assertIdentical($config->get('404'), $overrides['config_test.system']['404']);
 
     // Save the configuration object (having overrides applied).
     $config->save();
 
-    // Reload it and verify that it still contains overridden data from $conf.
+    // Reload it and verify that it still contains overridden data from $config.
     $config = \Drupal::config('config_test.system');
-    $this->assertIdentical($config->get('foo'), $conf['config_test.system']['foo']);
-    $this->assertIdentical($config->get('baz'), $conf['config_test.system']['baz']);
-    $this->assertIdentical($config->get('404'), $conf['config_test.system']['404']);
+    $this->assertIdentical($config->get('foo'), $overrides['config_test.system']['foo']);
+    $this->assertIdentical($config->get('baz'), $overrides['config_test.system']['baz']);
+    $this->assertIdentical($config->get('404'), $overrides['config_test.system']['404']);
 
     // Enter an override-free context to ensure the original data remains saved.
     config_context_enter('config.context.free');
@@ -128,9 +128,9 @@ function testConfOverride() {
 
     // Verifiy the overrides are still working.
     $config = \Drupal::config('config_test.system');
-    $this->assertIdentical($config->get('foo'), $conf['config_test.system']['foo']);
-    $this->assertIdentical($config->get('baz'), $conf['config_test.system']['baz']);
-    $this->assertIdentical($config->get('404'), $conf['config_test.system']['404']);
+    $this->assertIdentical($config->get('foo'), $overrides['config_test.system']['foo']);
+    $this->assertIdentical($config->get('baz'), $overrides['config_test.system']['baz']);
+    $this->assertIdentical($config->get('404'), $overrides['config_test.system']['404']);
   }
 
 }
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
index 879ca80..0e9327e 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
@@ -142,7 +142,6 @@ protected function tearDown() {
    * @see \DrupalUnitTestBase::disableModules()
    */
   public function containerBuild(ContainerBuilder $container) {
-    global $conf;
     // Keep the container object around for tests.
     $this->container = $container;
 
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
index 9e7b6b2..9ac43d5 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
@@ -11,6 +11,7 @@
 use Drupal\Core\Database\Database;
 use Drupal\Component\Utility\Settings;
 use Drupal\Core\Config\ConfigImporter;
+use Drupal\Core\Config\GlobalConfig;
 use Drupal\Core\Config\StorageComparer;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Core\Database\ConnectionNotDefinedException;
@@ -99,11 +100,23 @@
   protected $setupEnvironment = FALSE;
 
   /**
+   * Test-specific global configuration override values.
+   *
+   * @var array
+   */
+  protected $configOverrides = array();
+
+  /**
+   * @var \Drupal\Core\Config\GlobalConfig
+   */
+  protected $globalConfig;
+
+  /**
    * TRUE if verbose debugging is enabled.
    *
    * @var boolean
    */
-  protected $verbose = FALSE;
+  public $verbose = FALSE;
 
   /**
    * Incrementing identifier for verbose output filenames.
@@ -216,11 +229,6 @@ public static function getInfo() {
   }
 
   /**
-   * Performs setup tasks before each individual test method is run.
-   */
-  abstract protected function setUp();
-
-  /**
    * Checks the matching requirements for Test.
    *
    * @return
@@ -736,7 +744,7 @@ public function run(array $methods = array()) {
     $simpletest_config = \Drupal::config('simpletest.settings');
 
     $class = get_class($this);
-    if ($simpletest_config->get('verbose')) {
+    if ($this->verbose || $simpletest_config->get('verbose')) {
       // Initialize verbose debugging.
       $this->verbose = TRUE;
       $this->verboseDirectory = PublicStream::basePath() . '/simpletest/verbose';
@@ -898,7 +906,7 @@ protected function changeDatabasePrefix() {
    * @see TestBase::tearDown()
    */
   protected function prepareEnvironment() {
-    global $user, $conf;
+    global $user;
     $language_interface = language(Language::TYPE_INTERFACE);
 
     // When running the test runner within a test, back up the original database
@@ -908,9 +916,11 @@ protected function prepareEnvironment() {
       drupal_valid_test_ua($this->databasePrefix);
     }
 
+    $this->globalConfig = GlobalConfig::getInstance();
+
     // Backup current in-memory configuration.
     $this->originalSettings = settings()->getAll();
-    $this->originalConf = $conf;
+    $this->originalConfig = $this->globalConfig->getAll();
 
     // Backup statics and globals.
     $this->originalContainer = clone \Drupal::getContainer();
@@ -1054,6 +1064,45 @@ protected function rebuildContainer() {
   }
 
   /**
+   * Performs setup tasks before each individual test method is run.
+   */
+  protected function setUp() {
+    // Create the database prefix for this test.
+    $this->prepareDatabasePrefix();
+
+    // Prepare the environment for running tests.
+    $this->prepareEnvironment();
+    if (!$this->setupEnvironment) {
+      throw new \RuntimeException('Failed to set up test environment.');
+    }
+
+    // Change the database prefix.
+    // All static variables need to be reset before the database prefix is
+    // changed, since \Drupal\Core\Utility\CacheArray implementations attempt to
+    // write back to persistent caches when they are destructed.
+    $this->changeDatabasePrefix();
+    if (!$this->setupDatabasePrefix) {
+      throw new \RuntimeException('Failed to set up database prefix.');
+    }
+
+    // After preparing the environment and changing the database prefix, we are
+    // in a valid test environment.
+    drupal_valid_test_ua($this->databasePrefix);
+
+    // Remove all configuration overrides.
+    $this->globalConfig->setConfig(array());
+
+    // Apply global configuration override values.
+    foreach ($this->configOverrides as $config_name => $config_values) {
+      foreach ($config_values as $key => $value) {
+        $this->globalConfig->set($config_name, $key, $value);
+      }
+    }
+
+    $this->setup = TRUE;
+  }
+
+  /**
    * Performs cleanup tasks after each individual test method has been run.
    *
    * Deletes created files, database tables, and reverts environment changes.
@@ -1065,7 +1114,7 @@ protected function rebuildContainer() {
    * @see TestBase::prepareEnvironment()
    */
   protected function tearDown() {
-    global $user, $conf;
+    global $user;
 
     // Reset all static variables.
     // Unsetting static variables will potentially invoke destruct methods,
@@ -1128,15 +1177,19 @@ protected function tearDown() {
     drupal_static_reset();
 
     // Restore original in-memory configuration.
-    $conf = $this->originalConf;
+    $this->globalConfig->setConfig($this->originalConfig);
     new Settings($this->originalSettings);
 
     // Restore original statics and globals.
     \Drupal::setContainer($this->originalContainer);
     $GLOBALS['config_directories'] = $this->originalConfigDirectories;
+
     if (isset($this->originalPrefix)) {
       drupal_valid_test_ua($this->originalPrefix);
     }
+    else {
+      drupal_valid_test_ua(FALSE);
+    }
 
     // Restore original shutdown callbacks.
     $callbacks = &drupal_register_shutdown_function();
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/Tests/MissingCheckedRequirementsTest.php b/core/modules/simpletest/lib/Drupal/simpletest/Tests/MissingCheckedRequirementsTest.php
index 61d6401..8725e88 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/Tests/MissingCheckedRequirementsTest.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/Tests/MissingCheckedRequirementsTest.php
@@ -39,7 +39,7 @@ function setUp() {
    * Overrides checkRequirements().
    */
   protected function checkRequirements() {
-    if (drupal_valid_test_ua()) {
+    if (!empty($GLOBALS['drupal_test_info']['in_child_site'])) {
       return array(
         'Test is not allowed to run.'
       );
@@ -53,7 +53,7 @@ protected function checkRequirements() {
   protected function testCheckRequirements() {
     // If this is the main request, run the web test script and then assert
     // that the child tests did not run.
-    if (!drupal_valid_test_ua()) {
+    if (empty($GLOBALS['drupal_test_info']['in_child_site'])) {
       // Run this test from web interface.
       $edit['Drupal\simpletest\Tests\MissingCheckedRequirementsTest'] = TRUE;
       $this->drupalPostForm('admin/config/development/testing', $edit, t('Run tests'));
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/Tests/SimpleTestTest.php b/core/modules/simpletest/lib/Drupal/simpletest/Tests/SimpleTestTest.php
index 2a19a5c1..e830297 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/Tests/SimpleTestTest.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/Tests/SimpleTestTest.php
@@ -339,6 +339,6 @@ function asText(\SimpleXMLElement $element) {
    * Check if the test is being run from inside a CURL request.
    */
   function inCURL() {
-    return (bool) drupal_valid_test_ua();
+    return (bool) !empty($GLOBALS['drupal_test_info']['in_child_site']);
   }
 }
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/UnitTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/UnitTestBase.php
index 5510aa4..7f20fed 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/UnitTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/UnitTestBase.php
@@ -41,32 +41,8 @@ function __construct($test_id = NULL) {
    * setUp() method.
    */
   protected function setUp() {
-    global $conf;
-
-    // Create the database prefix for this test.
-    $this->prepareDatabasePrefix();
-
-    // Prepare the environment for running tests.
-    $this->prepareEnvironment();
-    if (!$this->setupEnvironment) {
-      return FALSE;
-    }
-
-    // Reset all statics and variables to perform tests in a clean environment.
-    $conf = array();
-    drupal_static_reset();
+    parent::setUp();
 
     $this->settingsSet('file_public_path', $this->public_files_directory);
-
-    // Change the database prefix.
-    // All static variables need to be reset before the database prefix is
-    // changed, since \Drupal\Core\Utility\CacheArray implementations attempt to
-    // write back to persistent caches when they are destructed.
-    $this->changeDatabasePrefix();
-    if (!$this->setupDatabasePrefix) {
-      return FALSE;
-    }
-
-    $this->setup = TRUE;
   }
 }
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
index 265012e..90bb51b 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
@@ -717,8 +717,6 @@ protected function drupalLogout() {
    * @see \Drupal\simpletest\WebTestBase::prepareEnvironment()
    */
   protected function setUp() {
-    global $conf;
-
     // When running tests through the Simpletest UI (vs. on the command line),
     // Simpletest's batch conflicts with the installer's batch. Batch API does
     // not support the concept of nested batches (in which the nested is not
@@ -726,32 +724,11 @@ protected function setUp() {
     // Backup the currently running Simpletest batch.
     $this->originalBatch = batch_get();
 
-    // Create the database prefix for this test.
-    $this->prepareDatabasePrefix();
-
-    // Prepare the environment for running tests.
-    $this->prepareEnvironment();
-    if (!$this->setupEnvironment) {
-      return FALSE;
-    }
-
-    // Reset all statics and variables to perform tests in a clean environment.
-    $conf = array();
-    drupal_static_reset();
+    parent::setUp();
 
-    // Change the database prefix.
-    // All static variables need to be reset before the database prefix is
-    // changed, since \Drupal\Core\Utility\CacheArray implementations attempt to
-    // write back to persistent caches when they are destructed.
-    $this->changeDatabasePrefix();
-    if (!$this->setupDatabasePrefix) {
-      return FALSE;
-    }
-
-    // Set the 'simpletest_parent_profile' variable to add the parent profile's
-    // search path to the child site's search paths.
+    // Add the parent profile's search path to the child site's search paths.
     // @see drupal_system_listing()
-    $conf['simpletest_parent_profile'] = $this->originalProfile;
+    $this->globalConfig->set('simpletest.settings', 'parent_profile', $this->originalProfile);
 
     // Define information about the user 1 account.
     $this->root_user = new UserSession(array(
@@ -764,21 +741,12 @@ protected function setUp() {
     // Reset the static batch to remove Simpletest's batch operations.
     $batch = &batch_get();
     $batch = array();
-    $variable_groups = array(
-      'system.file' => array(
-        'path.private' =>  $this->private_files_directory,
-        'path.temporary' =>  $this->temp_files_directory,
-      ),
-      'locale.settings' =>  array(
-        'translation.path' => $this->translation_files_directory,
-      ),
-    );
-    foreach ($variable_groups as $config_base => $variables) {
-      foreach ($variables as $name => $value) {
-        NestedArray::setValue($GLOBALS['conf'], array_merge(array($config_base), explode('.', $name)), $value);
-      }
-    }
+
     $this->settingsSet('file_public_path', $this->public_files_directory);
+    $this->globalConfig->set('system.file', 'path.private', $this->private_files_directory);
+    $this->globalConfig->set('system.file', 'path.temporary', $this->temp_files_directory);
+    $this->globalConfig->set('locale.settings', 'translation.path', $this->translation_files_directory);
+
     // Execute the non-interactive installer.
     require_once DRUPAL_ROOT . '/core/includes/install.core.inc';
     $this->settingsSet('cache', array('default' => 'cache.backend.memory'));
@@ -787,13 +755,9 @@ protected function setUp() {
 
     // Set the install_profile so that web requests to the requests to the child
     // site have the correct profile.
-    $settings = array(
-      'settings' => array(
-        'install_profile' => (object) array(
-          'value' => $this->profile,
-          'required' => TRUE,
-        ),
-      ),
+    $settings['settings']['install_profile'] = (object) array(
+      'value' => $this->profile,
+      'required' => TRUE,
     );
     $this->writeSettings($settings);
     // Override install profile in Settings to so the correct profile is used by
@@ -835,13 +799,13 @@ protected function setUp() {
 
     // Now make sure that the file path configurations are saved. This is done
     // after we install the modules to override default values.
-    foreach ($variable_groups as $config_base => $variables) {
-      $config = \Drupal::config($config_base);
-      foreach ($variables as $name => $value) {
-        $config->set($name, $value);
-      }
-      $config->save();
-    }
+    \Drupal::config('system.file')
+      ->set('path.private', $this->private_files_directory)
+      ->set('path.temporary', $this->temp_files_directory)
+      ->save();
+    \Drupal::config('locale.settings')
+      ->set('translation.path', $this->translation_files_directory)
+      ->save();
 
     // Use the test mail class instead of the default mail handler class.
     \Drupal::config('system.mail')->set('interface.default', 'Drupal\Core\Mail\TestMailCollector')->save();
diff --git a/core/modules/system/lib/Drupal/system/Tests/Installer/InstallerLanguageTest.php b/core/modules/system/lib/Drupal/system/Tests/Installer/InstallerLanguageTest.php
index c3308f7..f489ddb 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Installer/InstallerLanguageTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Installer/InstallerLanguageTest.php
@@ -24,11 +24,10 @@ public static function getInfo() {
   }
 
   function setUp() {
+    // Override the installation translations directory path.
+    $this->configOverrides['locale.settings']['translation.path'] = drupal_get_path('module', 'simpletest') . '/files/translations';
+
     parent::setUp();
-    // The database is not available during this part of install. Use global
-    // $conf to override the installation translations directory path.
-    global $conf;
-    $conf['locale.settings']['translation.path'] =  drupal_get_path('module', 'simpletest') . '/files/translations';
   }
 
   /**
@@ -44,7 +43,7 @@ function testInstallerTranslationFiles() {
       'it' => array(),
     );
 
-    $file_translation = new FileTranslation($GLOBALS['conf']['locale.settings']['translation.path']);
+    $file_translation = new FileTranslation($this->configOverrides['locale.settings']['translation.path']);
     foreach ($expected_translation_files as $langcode => $files_expected) {
       $files_found = $file_translation->findTranslationFiles($langcode);
       $this->assertTrue(count($files_found) == count($files_expected), format_string('@count installer languages found.', array('@count' => count($files_expected))));
diff --git a/core/modules/system/lib/Drupal/system/Tests/Installer/InstallerTranslationTest.php b/core/modules/system/lib/Drupal/system/Tests/Installer/InstallerTranslationTest.php
index 69b3352..7591381 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Installer/InstallerTranslationTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Installer/InstallerTranslationTest.php
@@ -24,8 +24,6 @@ public static function getInfo() {
   }
 
   protected function setUp() {
-    global $conf;
-
     // When running tests through the SimpleTest UI (vs. on the command line),
     // SimpleTest's batch conflicts with the installer's batch. Batch API does
     // not support the concept of nested batches (in which the nested is not
@@ -33,46 +31,35 @@ protected function setUp() {
     // Back up the currently running SimpleTest batch.
     $this->originalBatch = batch_get();
 
-    // Add the translations directory so we can retrieve German translations.
-    $conf['locale.settings']['translation.path'] = drupal_get_path('module', 'simpletest') . '/files/translations';
-    $conf['language_default']['name'] = 'German';
-    $conf['language_default']['id'] = 'de';
-
     // Create the database prefix for this test.
     $this->prepareDatabasePrefix();
 
     // Prepare the environment for running tests.
     $this->prepareEnvironment();
     if (!$this->setupEnvironment) {
-      return FALSE;
+      throw new \RuntimeException('Failed to set up test environment.');
     }
 
-    // Reset all statics and variables to perform tests in a clean environment.
-    $conf = array();
-    drupal_static_reset();
-
     // Change the database prefix.
     // All static variables need to be reset before the database prefix is
     // changed, since \Drupal\Core\Utility\CacheArray implementations attempt to
     // write back to persistent caches when they are destructed.
     $this->changeDatabasePrefix();
     if (!$this->setupDatabasePrefix) {
-      return FALSE;
-    }
-    $variable_groups = array(
-      'system.file' => array(
-        'path.private' =>  $this->private_files_directory,
-        'path.temporary' => $this->temp_files_directory,
-      ),
-      'locale.settings' => array(
-        'translation.path' => $this->translation_files_directory,
-      ),
-    );
-    foreach ($variable_groups as $config_base => $variables) {
-      foreach ($variables as $name => $value) {
-        NestedArray::setValue($GLOBALS['conf'], array_merge(array($config_base), explode('.', $name)), $value);
-      }
+      throw new \RuntimeException('Failed to set up database prefix.');
     }
+
+    // After preparing the environment and changing the database prefix, we are
+    // in a valid test environment.
+    drupal_valid_test_ua($this->databasePrefix);
+
+    // Remove all configuration overrides.
+    $this->globalConfig->setConfig(array());
+
+    $this->globalConfig->set('system.file', 'path.private', $this->private_files_directory);
+    $this->globalConfig->set('system.file', 'path.temporary', $this->temp_files_directory);
+    $this->globalConfig->set('locale.settings', 'translation.path', $this->translation_files_directory);
+
     $settings['conf_path'] = (object) array(
       'value' => $this->public_files_directory,
       'required' => TRUE,
@@ -81,10 +68,31 @@ protected function setUp() {
       'value' => array(),
       'required' => TRUE,
     );
+    $settings['config']['system.file'] = (object) array(
+      'value' => array(
+        'path' => array(
+          'private' => $this->private_files_directory,
+          'temporary' => $this->temp_files_directory,
+        ),
+      ),
+      'required' => TRUE,
+    );
+    // Add the translations directory so we can retrieve German translations.
+    $settings['config']['locale.settings'] = (object) array(
+      'value' => array(
+        'translation' => array(
+          'path' => drupal_get_path('module', 'simpletest') . '/files/translations',
+        ),
+      ),
+      'required' => TRUE,
+    );
     $this->writeSettings($settings);
 
     // Submit the installer with German language.
-    $this->drupalPostForm($GLOBALS['base_url'] . '/core/install.php', array('langcode' => 'de'), 'Save and continue');
+    $edit = array(
+      'langcode' => 'de',
+    );
+    $this->drupalPostForm($GLOBALS['base_url'] . '/core/install.php', $edit, 'Save and continue');
 
     // On the following page where installation profile is being selected the
     // interface should be already translated, so there is no "Set up database"
@@ -99,9 +107,13 @@ protected function setUp() {
     // Get the "Save and continue" submit button translated value from the
     // translated interface.
     $submit_value = (string) current($this->xpath('//input[@type="submit"]/@value'));
+    $this->assertNotEqual($submit_value, 'Save and continue');
 
-    // Submit the standard profile installation.
-    $this->drupalPostForm(NULL, array('profile' => 'standard'), $submit_value);
+    // Submit the Minimal profile installation.
+    $edit = array(
+      'profile' => 'minimal',
+    );
+    $this->drupalPostForm(NULL, $edit, $submit_value);
 
     // Submit the next step.
     $this->drupalPostForm(NULL, array(), $submit_value);
@@ -113,13 +125,13 @@ protected function setUp() {
     }
     $this->rebuildContainer();
 
-    foreach ($variable_groups as $config_base => $variables) {
-      $config = \Drupal::config($config_base);
-      foreach ($variables as $name => $value) {
-        $config->set($name, $value);
-      }
-      $config->save();
-    }
+    \Drupal::config('system.file')
+      ->set('path.private', $this->private_files_directory)
+      ->set('path.temporary', $this->temp_files_directory)
+      ->save();
+    \Drupal::config('locale.settings')
+      ->set('translation.path', $this->translation_files_directory)
+      ->save();
 
     // Submit site configuration form.
     $this->drupalPostForm(NULL, array(
diff --git a/core/modules/system/lib/Drupal/system/Tests/InstallerTest.php b/core/modules/system/lib/Drupal/system/Tests/InstallerTest.php
index 5bbaab8..2ae1f78 100644
--- a/core/modules/system/lib/Drupal/system/Tests/InstallerTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/InstallerTest.php
@@ -24,8 +24,6 @@ public static function getInfo() {
   }
 
   protected function setUp() {
-    global $conf;
-
     // When running tests through the SimpleTest UI (vs. on the command line),
     // SimpleTest's batch conflicts with the installer's batch. Batch API does
     // not support the concept of nested batches (in which the nested is not
@@ -39,35 +37,29 @@ protected function setUp() {
     // Prepare the environment for running tests.
     $this->prepareEnvironment();
     if (!$this->setupEnvironment) {
-      return FALSE;
+      throw new \RuntimeException('Failed to set up test environment.');
     }
 
-    // Reset all statics and variables to perform tests in a clean environment.
-    $conf = array();
-    drupal_static_reset();
-
     // Change the database prefix.
     // All static variables need to be reset before the database prefix is
     // changed, since \Drupal\Core\Utility\CacheArray implementations attempt to
     // write back to persistent caches when they are destructed.
     $this->changeDatabasePrefix();
     if (!$this->setupDatabasePrefix) {
-      return FALSE;
-    }
-    $variable_groups = array(
-      'system.file' => array(
-        'path.private' =>  $this->private_files_directory,
-        'path.temporary' =>  $this->temp_files_directory,
-      ),
-      'locale.settings' =>  array(
-        'translation.path' => $this->translation_files_directory,
-      ),
-    );
-    foreach ($variable_groups as $config_base => $variables) {
-      foreach ($variables as $name => $value) {
-        NestedArray::setValue($GLOBALS['conf'], array_merge(array($config_base), explode('.', $name)), $value);
-      }
+      throw new \RuntimeException('Failed to set up database prefix.');
     }
+
+    // After preparing the environment and changing the database prefix, we are
+    // in a valid test environment.
+    drupal_valid_test_ua($this->databasePrefix);
+
+    // Remove all configuration overrides.
+    $this->globalConfig->setConfig(array());
+
+    $this->globalConfig->set('system.file', 'path.private', $this->private_files_directory);
+    $this->globalConfig->set('system.file', 'path.temporary', $this->temp_files_directory);
+    $this->globalConfig->set('locale.settings', 'translation.path', $this->translation_files_directory);
+
     $settings['conf_path'] = (object) array(
       'value' => $this->public_files_directory,
       'required' => TRUE,
@@ -76,6 +68,23 @@ protected function setUp() {
       'value' => array(),
       'required' => TRUE,
     );
+    $settings['config']['system.file'] = (object) array(
+      'value' => array(
+        'path' => array(
+          'private' => $this->private_files_directory,
+          'temporary' => $this->temp_files_directory,
+        ),
+      ),
+      'required' => TRUE,
+    );
+    $settings['config']['locale.settings'] = (object) array(
+      'value' => array(
+        'translation' => array(
+          'path' => $this->translation_files_directory,
+        ),
+      ),
+      'required' => TRUE,
+    );
     $this->writeSettings($settings);
 
     $this->drupalGet($GLOBALS['base_url'] . '/core/install.php?langcode=en&profile=minimal');
@@ -87,13 +96,13 @@ protected function setUp() {
     }
     $this->rebuildContainer();
 
-    foreach ($variable_groups as $config_base => $variables) {
-      $config = \Drupal::config($config_base);
-      foreach ($variables as $name => $value) {
-        $config->set($name, $value);
-      }
-      $config->save();
-    }
+    \Drupal::config('system.file')
+      ->set('path.private', $this->private_files_directory)
+      ->set('path.temporary', $this->temp_files_directory)
+      ->save();
+    \Drupal::config('locale.settings')
+      ->set('translation.path', $this->translation_files_directory)
+      ->save();
 
     // Use the test mail class instead of the default mail handler class.
     \Drupal::config('system.mail')->set('interface.default', 'Drupal\Core\Mail\TestMailCollector')->save();
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 34d8dde..29b8f34 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -320,7 +320,6 @@ function system_requirements($phase) {
   // During an install we need to make assumptions about the file system
   // unless overrides are provided in settings.php.
   if ($phase == 'install') {
-    global $conf;
     $directories = array();
     if ($file_public_path = settings()->get('file_public_path')) {
       $directories[] = $file_public_path;
@@ -331,11 +330,12 @@ function system_requirements($phase) {
       // conf_path() cache must also be reset in this case.
       $directories[] = conf_path(FALSE, TRUE) . '/files';
     }
-    if (!empty($conf['system.file']['path.private'])) {
-      $directories[] = $conf['system.file']['path.private'];
+    $config = \Drupal::config('system.file');
+    if ($config->get('path.private')) {
+      $directories[] = $config->get('path.private');
     }
-    if (!empty($conf['system.file']['path.temporary'])) {
-      $directories[] = $conf['system.file']['path.temporary'];
+    if ($config->get('path.temporary')) {
+      $directories[] = $config->get('path.temporary');
     }
     else {
       // If the temporary directory is not overridden use an appropriate
diff --git a/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
index e9f0ffe..8a7c0e2 100755
--- a/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -484,7 +484,7 @@ function simpletest_script_run_phpunit($test_id, $class) {
  * Bootstrap Drupal and run a single test.
  */
 function simpletest_script_run_one_test($test_id, $test_class) {
-  global $args, $conf;
+  global $args;
 
   try {
     // Bootstrap Drupal.
@@ -495,12 +495,9 @@ function simpletest_script_run_one_test($test_id, $test_class) {
     $container = \Drupal::getContainer();
     $container->set('request', $request);
 
-    // Override configuration according to command line parameters.
-    $conf['simpletest.settings']['verbose'] = $args['verbose'];
-    $conf['simpletest.settings']['clear_results'] = !$args['keep-results'];
-
     $test = new $test_class($test_id);
     $test->dieOnFail = (bool) $args['die-on-fail'];
+    $test->verbose = (bool) $args['verbose'];
     $test->run();
     $info = $test->getInfo();
 
diff --git a/sites/default/default.settings.php b/sites/default/default.settings.php
index 5a46b12..2160376 100644
--- a/sites/default/default.settings.php
+++ b/sites/default/default.settings.php
@@ -586,25 +586,19 @@
 # $cookie_domain = '.example.com';
 
 /**
- * Variable overrides:
+ * Configuration overrides.
  *
- * To override specific entries in the 'variable' table for this site,
+ * To globally override specific configuration values for this site,
  * set them here. You usually don't need to use this feature. This is
  * useful in a configuration file for a vhost or directory, rather than
- * the default settings.php. Any configuration setting from the 'variable'
- * table can be given a new value. Note that any values you provide in
- * these variable overrides will not be modifiable from the Drupal
- * administration interface.
- *
- * The following overrides are examples:
- * - site_name: Defines the site's name.
- * - $conf['system.theme']['default']: Defines the default theme for this site.
- * - anonymous: Defines the human-readable name of anonymous users.
- * Remove the leading hash signs to enable.
+ * the default settings.php.
+ *
+ * Note that any values you provide in these variable overrides will not be
+ * modifiable from the Drupal administration interface.
  */
-# $conf['system.site']['name'] = 'My Drupal site';
-# $conf['system.theme']['default'] = 'stark';
-# $conf['anonymous'] = 'Visitor';
+# $config['system.site']['name'] = 'My Drupal site';
+# $config['system.theme']['default'] = 'stark';
+# $config['user.settings']['anonymous'] = 'Visitor';
 
 /**
  * CSS/JS aggregated file gzip compression:
@@ -618,8 +612,8 @@
  * configured to cache and compress these files itself you may want to uncomment
  * one or both of the below lines, which will prevent gzip files being stored.
  */
-# $conf['system.performance']['css']['gzip'] = FALSE;
-# $conf['system.performance']['js']['gzip'] = FALSE;
+# $config['system.performance']['css']['gzip'] = FALSE;
+# $config['system.performance']['js']['gzip'] = FALSE;
 
 /**
  * Fast 404 pages:
@@ -643,9 +637,9 @@
  *
  * Remove the leading hash signs if you would like to alter this functionality.
  */
-#$conf['system.performance']['fast_404']['exclude_paths'] = '/\/(?:styles)\//';
-#$conf['system.performance']['fast_404']['paths'] = '/\.(?:txt|png|gif|jpe?g|css|js|ico|swf|flv|cgi|bat|pl|dll|exe|asp)$/i';
-#$conf['system.performance']['fast_404']['html'] = '<!DOCTYPE html><html><head><title>404 Not Found</title></head><body><h1>Not Found</h1><p>The requested URL "@path" was not found on this server.</p></body></html>';
+# $config['system.performance']['fast_404']['exclude_paths'] = '/\/(?:styles)\//';
+# $config['system.performance']['fast_404']['paths'] = '/\.(?:txt|png|gif|jpe?g|css|js|ico|swf|flv|cgi|bat|pl|dll|exe|asp)$/i';
+# $config['system.performance']['fast_404']['html'] = '<!DOCTYPE html><html><head><title>404 Not Found</title></head><body><h1>Not Found</h1><p>The requested URL "@path" was not found on this server.</p></body></html>';
 
 /**
  * Load local development override configuration, if available.