diff --git a/core/includes/schema.inc b/core/includes/schema.inc
index 4cf91ea..68afaca 100644
--- a/core/includes/schema.inc
+++ b/core/includes/schema.inc
@@ -340,18 +340,18 @@ function _drupal_schema_initialize(&$schema, $module, $remove_descriptions = TRU
  *   An array of fields.
  */
 function drupal_schema_fields_sql($table, $prefix = NULL) {
-  $schema = drupal_get_schema($table);
-  $fields = array_keys($schema['fields']);
-  if ($prefix) {
-    $columns = array();
-    foreach ($fields as $field) {
-      $columns[] = "$prefix.$field";
+  if ($schema = drupal_get_schema($table)) {
+    $fields = array_keys($schema['fields']);
+    if ($prefix) {
+      $columns = array();
+      foreach ($fields as $field) {
+        $columns[] = "$prefix.$field";
+      }
+      return $columns;
     }
-    return $columns;
-  }
-  else {
     return $fields;
   }
+  return array();
 }
 
 /**
diff --git a/core/modules/edit/lib/Drupal/edit/Tests/EditTestBase.php b/core/modules/edit/lib/Drupal/edit/Tests/EditTestBase.php
index 573ce93..813a3a3 100644
--- a/core/modules/edit/lib/Drupal/edit/Tests/EditTestBase.php
+++ b/core/modules/edit/lib/Drupal/edit/Tests/EditTestBase.php
@@ -20,7 +20,7 @@ class EditTestBase extends DrupalUnitTestBase {
    *
    * @var array
    */
-  public static $modules = array('system', 'entity', 'field_test', 'field', 'number', 'text', 'edit', 'edit_test');
+  public static $modules = array('system', 'entity', 'number', 'text', 'edit', 'edit_test');
 
   /**
    * Sets the default field storage backend for fields created during tests.
diff --git a/core/modules/forum/lib/Drupal/forum/Tests/ForumTest.php b/core/modules/forum/lib/Drupal/forum/Tests/ForumTest.php
index 7b0bef7..4390600 100644
--- a/core/modules/forum/lib/Drupal/forum/Tests/ForumTest.php
+++ b/core/modules/forum/lib/Drupal/forum/Tests/ForumTest.php
@@ -108,7 +108,7 @@ function testEnableForumField() {
     $edit['modules[Core][forum][enable]'] = FALSE;
     $this->drupalPost('admin/modules', $edit, t('Save configuration'));
     $this->assertText(t('The configuration options have been saved.'), 'Modules status has been updated.');
-    system_list_reset();
+    $this->rebuildContainer();
     $this->assertFalse(module_exists('forum'), 'Forum module is not enabled.');
 
     // Attempt to re-enable the Forum module and ensure it does not try to
@@ -117,7 +117,7 @@ function testEnableForumField() {
     $edit['modules[Core][forum][enable]'] = 'forum';
     $this->drupalPost('admin/modules', $edit, t('Save configuration'));
     $this->assertText(t('The configuration options have been saved.'), 'Modules status has been updated.');
-    system_list_reset();
+    $this->rebuildContainer();
     $this->assertTrue(module_exists('forum'), 'Forum module is enabled.');
   }
 
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
index d68c4ca..c806f43 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
@@ -50,7 +50,6 @@
    */
   public static $modules = array();
 
-  private $extension_handler;
   private $moduleFiles;
   private $themeFiles;
   private $themeData;
@@ -111,7 +110,6 @@ protected function setUp() {
       unset($install[$system]);
       array_unshift($install, 'system');
     }
-    $this->extension_handler = $this->container->get('extension_handler');
     if ($install) {
       $this->enableModules($install);
     }
@@ -215,20 +213,17 @@ protected function installSchema($module, $table) {
    */
   protected function enableModules(array $modules, $install = TRUE) {
     // Explicitly set the list of modules in the extension handler.
-    $enabled = $this->extension_handler->getModuleList();
+    $enabled = $this->container->get('extension_handler')->getModuleList();
     foreach ($modules as $module) {
       $enabled[$module] = drupal_get_filename('module', $module);
       // Call module_enable() to enable (install) the new module.
       if ($install) {
         module_enable(array($module), FALSE);
       }
-      $this->extension_handler->setModuleList($enabled);
-    }
-    // Otherwise, only ensure that the new modules are loaded.
-    if (!$install) {
-      module_load_all(FALSE, TRUE);
-      $this->extension_handler->moduleImplementsReset();
+      $this->container->get('extension_handler')->setModuleList($enabled);
     }
+    $this->container->get('extension_handler')->moduleImplementsReset();
+    $this->container->get('extension_handler')->loadAll(FALSE, TRUE);
   }
 
 }