diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 9c78d68..673648a 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -429,6 +429,11 @@ function conf_path($require_settings = TRUE, $reset = FALSE) {
   if ($conf && !$reset) {
     return $conf;
   }
+  // Keep the conf_path alive across drupal_static_reset() calls.
+  if (class_exists('Drupal\\Component\\Utility\\Settings') && ($simpletest_conf_path = settings()->get('simpletest_conf_path'))) {
+    $conf = $simpletest_conf_path;
+    return $conf;
+  }
 
   $script_name = $_SERVER['SCRIPT_NAME'];
   if (!$script_name) {
@@ -2604,7 +2609,7 @@ function drupal_valid_test_ua($new_prefix = NULL) {
     // and the HMAC must match.
     if ($time_diff >= 0 && $time_diff <= 5 && $hmac == drupal_hmac_base64($check_string, $key)) {
       $test_prefix = $prefix;
-      _drupal_test_overrides($test_prefix, $config);
+      _drupal_load_test_overrides($test_prefix, $config);
       return $test_prefix;
     }
   }
@@ -2614,9 +2619,11 @@ function drupal_valid_test_ua($new_prefix = NULL) {
 }
 
 /**
+ * Overrides some very basic settings.
+ *
  * Very strictly for internal use only.
  *
- * Loads override.php and settings.php from the simpletest public files
+ * Loads settings.php from the simpletest public files
  * directory. These files can change the global $conf, the global
  * $config_directories, the return value of conf_path() and
  * settings().
@@ -2628,7 +2635,7 @@ function drupal_valid_test_ua($new_prefix = NULL) {
  *   directory as config directories. N to start with empty
  *   $config_directories.
  */
-function _drupal_test_overrides($test_prefix, $config) {
+function _drupal_load_test_overrides($test_prefix, $config) {
   global $conf, $config_directories;
   $path_prefix = 'simpletest/' . substr($test_prefix, 10);
   if ($config === 'Y') {
@@ -2639,25 +2646,23 @@ function _drupal_test_overrides($test_prefix, $config) {
   else {
     $config_directories = array();
   }
-  $dir = conf_path() . '/files/' . $path_prefix;
-  $filename = $dir . '/override.php';
+  $filename = conf_path() . '/files/' . $path_prefix . '/settings.php';
   if (file_exists($filename)) {
     $settings = settings()->getAll();
     $conf_path = &drupal_static('conf_path');
-    // This can override $conf, $conf_path and $settings.
+    // This can override $conf, $conf_path, $settings and
+    // $config_directories
     include $filename;
+    // Keep the conf_path alive across drupal_static_reset() calls.
+    $settings['simpletest_conf_path'] = $conf_path;
     new Settings($settings);
   }
-  $filename = $dir . '/settings.php';
-  if (file_exists($filename)) {
-    include $filename;
-  }
 }
 
 /**
  * Generates a user agent string with a HMAC and timestamp for simpletest.
  */
-function drupal_generate_test_ua($prefix, $config = 'Y') {
+function drupal_generate_test_ua($prefix, $config = TRUE) {
   global $drupal_hash_salt;
   static $key;
 
@@ -2670,7 +2675,7 @@ function drupal_generate_test_ua($prefix, $config = 'Y') {
   // Generate a moderately secure HMAC based on the database credentials.
   $salt = uniqid('', TRUE);
   $check_string = $prefix . ';' . time() . ';' . $salt;
-  return $check_string . ';' . drupal_hmac_base64($check_string, $key) . $config;
+  return $check_string . ';' . drupal_hmac_base64($check_string, $key) . ($config ? 'Y' : 'N');
 }
 
 /**
diff --git a/core/includes/update.inc b/core/includes/update.inc
index c0d0eee..6aea70f 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -107,6 +107,7 @@ function update_prepare_d8_bootstrap() {
 
   // Check whether settings.php needs to be rewritten.
   $settings_exist = !empty($GLOBALS['config_directories']);
+
   if (!$settings_exist || !is_dir(config_get_config_directory('active')) || !is_dir(config_get_config_directory('staging'))) {
     drupal_install_config_directories();
   }
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
index 99dc276..119c148 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
@@ -163,7 +163,7 @@
    *   Set to N if you want the child Drupal to not use the pregenerated
    *   config directory path.
    */
-  protected $pregeneratedConfigDirectories = 'Y';
+  protected $pregeneratedConfigDirectories = TRUE;
 
   /**
    * Constructor for Drupal\simpletest\WebTestBase.
diff --git a/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalAnonymousUpgradePathTest.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalAnonymousUpgradePathTest.php
index b25e848..6299c57 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalAnonymousUpgradePathTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalAnonymousUpgradePathTest.php
@@ -6,28 +6,37 @@
 
 namespace Drupal\system\Tests\Upgrade;
 
-
+/**
+ * Tests the database upgrade path without logging into Drupal 7 first.
+ */
 class BareMinimalAnonymousUpgradePathTest extends BareMinimalUpgradePathTest {
   public static function getInfo() {
     return array(
-      'name'  => 'Basic minimal profile upgrade, free access',
-      'description'  => 'Basic upgrade path tests for a minimal profile install with a bare database and update_free_access set to TRUE.',
+      'name' => 'Basic minimal profile upgrade, free access',
+      'description' => 'Basic upgrade path tests for a minimal profile install with a bare database and update_free_access set to TRUE.',
       'group' => 'Upgrade path',
     );
   }
 
+  /**
+   * Overrides \Drupal\system\Tests\Upgrade\UpgradePathTestBase::prepareD8Session().
+   */
   protected function prepareD8Session() {
     $new_settings['settings']['update_free_access'] = (object) array(
       'value' => TRUE,
       'required' => TRUE,
     );
     include_once DRUPAL_ROOT . '/core/includes/install.inc';
-    $filename = $this->public_files_directory . '/override.php';
+    $filename = $this->public_files_directory . '/settings.php';
     file_put_contents($filename, "<?php\n");
     drupal_rewrite_settings($new_settings, $filename);
   }
 
-  protected function assertStillLoggedin() {
-    // We are not logged in, nothing to assert.
+  /**
+   * Overrides \Drupal\system\Tests\Upgrade\UpgradePathTestBase::assertSessionKept().
+   */
+  protected function assertSessionKept() {
+    // We are not logged in, nothing to do.
   }
+
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalNoConfigUpgradePathTest.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalNoConfigUpgradePathTest.php
index 6891b9e..994ee17 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalNoConfigUpgradePathTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalNoConfigUpgradePathTest.php
@@ -1,15 +1,15 @@
 <?php
 /**
- * Definition of Drupal\system\Tests\Upgrade\BareMinimalNoConfigUpgradePathTest.
+ * Contains \Drupal\system\Tests\Upgrade\BareMinimalNoConfigUpgradePathTest.
  */
 
 namespace Drupal\system\Tests\Upgrade;
 
-
+/**
+ * Tests the database upgrade path without creating config directories.
+ */
 class BareMinimalNoConfigUpgradePathTest extends BareMinimalUpgradePathTest {
 
-  protected $configDirectoriesSet;
-
   public static function getInfo() {
     return array(
       'name'  => 'Basic minimal profile upgrade, no config',
@@ -18,32 +18,35 @@ public static function getInfo() {
     );
   }
 
+  /**
+   * Overrides \Drupal\system\Tests\Upgrade\UpgradePathTestBase::prepareConfigDirectories().
+   */
   protected function prepareConfigDirectories() {
     $new_settings['conf_path'] = (object) array(
       'value' => $this->public_files_directory,
       'required' => TRUE,
     );
     include_once DRUPAL_ROOT . '/core/includes/install.inc';
-    $filename = $this->public_files_directory . '/override.php';
+    $filename = $this->public_files_directory . '/settings.php';
     file_put_contents($filename, "<?php\n");
     drupal_rewrite_settings($new_settings, $filename);
-    file_put_contents($this->public_files_directory . '/settings.php', "<?php\n");
-    $this->pregeneratedConfigDirectories = 'N';
-    $this->configDirectoriesSet = TRUE;
+    $this->pregeneratedConfigDirectories = FALSE;
   }
 
+  /**
+   * Overrides \Drupal\system\Tests\Upgrade\UpgradePathTestBase::refreshVariables().
+   */
   protected function refreshVariables() {
     // Refresh the variables only if the site was already upgraded.
-    if ($this->upgradedSite && $this->configDirectoriesSet) {
-      $this->configDirectoriesSet = FALSE;
+    if ($this->upgradedSite) {
+      // update.php puts the new, randomized config directries in this file.
       include $this->public_files_directory . '/settings.php';
       $GLOBALS['config_directories'] = array();
-      include_once DRUPAL_ROOT . '/core/includes/install.inc';
       foreach ($config_directories as $type => $data) {
         $GLOBALS['config_directories'][$type]['path'] = 'simpletest/' . substr($this->databasePrefix, 10) . '/files/' . $data['path'];
       }
+      parent::refreshVariables();
     }
-    parent::refreshVariables();
   }
 
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalUpgradePathTest.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalUpgradePathTest.php
index 7f1abdd..1156616 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalUpgradePathTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/BareMinimalUpgradePathTest.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Definition of Drupal\system\Tests\Upgrade\BareMinimalUpgradePathTest.
+ * Contains \Drupal\system\Tests\Upgrade\BareMinimalUpgradePathTest.
  */
 
 namespace Drupal\system\Tests\Upgrade;
@@ -43,7 +43,7 @@ public function testBasicMinimalUpgrade() {
     $this->assertResponse(200);
 
     // Verify that we are still logged in.
-    $this->assertStillLoggedIn();
+    $this->assertSessionKept();
     $this->drupalLogin((object) array(
       'uid' => 1,
       'name' => 'admin',
@@ -91,14 +91,13 @@ public function testBasicMinimalUpgrade() {
   }
 
   /**
-   * Assert that we are still logged in.
+   * Assert that the session was kept during update. Also, log out.
    */
-  protected function assertStillLoggedin() {
+  protected function assertSessionKept() {
     $this->drupalGet('user');
     $this->clickLink(t('Edit'));
     $this->assertEqual($this->getUrl(), url('user/1/edit', array('absolute' => TRUE)), 'We are still logged in as admin at the end of the upgrade.');
-
-    // Logout and verify that we can login back in with our initial password.
     $this->drupalLogout();
   }
+
 }