diff --git a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
index b98085b..8111e17 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
@@ -144,16 +144,16 @@ protected function setUp() {
     // In order to use theme functions default theme config needs to exist.
     \Drupal::config('system.theme')->set('default', 'stark');
 
-    // Tests based on DrupalUnitTestBase are entitled to use Drupal's File API.
+    // Tests based on this class are entitled to use Drupal's File and
+    // StreamWrapper APIs.
+    // @todo Move StreamWrapper management into DrupalKernel.
+    // @see https://drupal.org/node/2028109
+    // The public stream wrapper only depends on the file_public_path setting,
+    // which is provided by UnitTestBase::setUp().
     $this->registerStreamWrapper('public', 'Drupal\Core\StreamWrapper\PublicStream');
-
-    // The private and temporary stream wrappers depend on the system.file
-    // configuration. If System module was enabled, the test will most likely
-    // install System module's configuration, so we can register them here.
-    if (in_array('system', $modules)) {
-      $this->registerStreamWrapper('private', 'Drupal\Core\StreamWrapper\PrivateStream');
-      $this->registerStreamWrapper('temporary', 'Drupal\Core\StreamWrapper\TemporaryStream');
-    }
+    // The temporary stream wrapper is able to operate both with and without
+    // configuration.
+    $this->registerStreamWrapper('temporary', 'Drupal\Core\StreamWrapper\TemporaryStream');
   }
 
   protected function tearDown() {
@@ -162,6 +162,8 @@ protected function tearDown() {
     // of this test leaks into the parent environment. Unlike all other global
     // state variables in Drupal, stream wrappers are a global state construct
     // of PHP core, which has to be maintained manually.
+    // @todo Move StreamWrapper management into DrupalKernel.
+    // @see https://drupal.org/node/2028109
     foreach ($this->streamWrappers as $scheme) {
       $this->unregisterStreamWrapper($scheme);
     }
@@ -391,6 +393,7 @@ protected function registerStreamWrapper($scheme, $class, $type = STREAM_WRAPPER
       stream_wrapper_register($scheme, $class, STREAM_IS_URL);
     }
     // @todo Revamp Drupal's stream wrapper API for D8.
+    // @see https://drupal.org/node/2028109
     $wrappers = &drupal_static('file_get_stream_wrappers');
     $wrappers[$scheme] = array(
       'type' => $type,
@@ -412,6 +415,7 @@ protected function unregisterStreamWrapper($scheme) {
     stream_wrapper_unregister($scheme);
     unset($this->streamWrappers[$scheme]);
     // @todo Revamp Drupal's stream wrapper API for D8.
+    // @see https://drupal.org/node/2028109
     $wrappers = &drupal_static('file_get_stream_wrappers');
     unset($wrappers[$scheme]);
     unset($wrappers[STREAM_WRAPPERS_ALL][$scheme]);
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/FileTestBase.php b/core/modules/system/lib/Drupal/system/Tests/File/FileTestBase.php
index 6857149..d3d913c 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/FileTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/FileTestBase.php
@@ -39,6 +39,7 @@
   function setUp() {
     parent::setUp();
     $this->installConfig(array('system'));
+    $this->registerStreamWrapper('private', 'Drupal\Core\StreamWrapper\PrivateStream');
 
     if (isset($this->scheme)) {
       $this->registerStreamWrapper($this->scheme, $this->classname);
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/ReadOnlyStreamWrapperTest.php b/core/modules/system/lib/Drupal/system/Tests/File/ReadOnlyStreamWrapperTest.php
index 779ba12..e02cd07 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/ReadOnlyStreamWrapperTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/ReadOnlyStreamWrapperTest.php
@@ -12,7 +12,18 @@
  */
 class ReadOnlyStreamWrapperTest extends FileTestBase {
 
+  /**
+   * A stream wrapper scheme to register for the test.
+   *
+   * @var string
+   */
   protected $scheme = 'dummy-readonly';
+
+  /**
+   * A fully-qualified stream wrapper class name to register for the test.
+   *
+   * @var string
+   */
   protected $classname = 'Drupal\file_test\DummyReadOnlyStreamWrapper';
 
   public static function getInfo() {
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileDirectoryTest.php b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileDirectoryTest.php
index af39312..55946b8 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileDirectoryTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileDirectoryTest.php
@@ -19,7 +19,18 @@ class RemoteFileDirectoryTest extends DirectoryTest {
    */
   public static $modules = array('file_test');
 
+  /**
+   * A stream wrapper scheme to register for the test.
+   *
+   * @var string
+   */
   protected $scheme = 'dummy-remote';
+
+  /**
+   * A fully-qualified stream wrapper class name to register for the test.
+   *
+   * @var string
+   */
   protected $classname = 'Drupal\file_test\DummyRemoteStreamWrapper';
 
   public static function getInfo() {
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileScanDirectoryTest.php b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileScanDirectoryTest.php
index 93e2016..ded05b4 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileScanDirectoryTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileScanDirectoryTest.php
@@ -19,7 +19,18 @@ class RemoteFileScanDirectoryTest extends ScanDirectoryTest {
    */
   public static $modules = array('file_test');
 
+  /**
+   * A stream wrapper scheme to register for the test.
+   *
+   * @var string
+   */
   protected $scheme = 'dummy-remote';
+
+  /**
+   * A fully-qualified stream wrapper class name to register for the test.
+   *
+   * @var string
+   */
   protected $classname = 'Drupal\file_test\DummyRemoteStreamWrapper';
 
   public static function getInfo() {
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedCopyTest.php b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedCopyTest.php
index d81213e..4bf8864 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedCopyTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedCopyTest.php
@@ -19,7 +19,18 @@ class RemoteFileUnmanagedCopyTest extends UnmanagedCopyTest {
    */
   public static $modules = array('file_test');
 
+  /**
+   * A stream wrapper scheme to register for the test.
+   *
+   * @var string
+   */
   protected $scheme = 'dummy-remote';
+
+  /**
+   * A fully-qualified stream wrapper class name to register for the test.
+   *
+   * @var string
+   */
   protected $classname = 'Drupal\file_test\DummyRemoteStreamWrapper';
 
   public static function getInfo() {
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedDeleteRecursiveTest.php b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedDeleteRecursiveTest.php
index a43c3a1..8cdc8d5 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedDeleteRecursiveTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedDeleteRecursiveTest.php
@@ -19,7 +19,18 @@ class RemoteFileUnmanagedDeleteRecursiveTest extends UnmanagedDeleteRecursiveTes
    */
   public static $modules = array('file_test');
 
+  /**
+   * A stream wrapper scheme to register for the test.
+   *
+   * @var string
+   */
   protected $scheme = 'dummy-remote';
+
+  /**
+   * A fully-qualified stream wrapper class name to register for the test.
+   *
+   * @var string
+   */
   protected $classname = 'Drupal\file_test\DummyRemoteStreamWrapper';
 
   public static function getInfo() {
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedDeleteTest.php b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedDeleteTest.php
index d6a9b07..f1105df 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedDeleteTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedDeleteTest.php
@@ -19,7 +19,18 @@ class RemoteFileUnmanagedDeleteTest extends UnmanagedDeleteTest {
    */
   public static $modules = array('file_test');
 
+  /**
+   * A stream wrapper scheme to register for the test.
+   *
+   * @var string
+   */
   protected $scheme = 'dummy-remote';
+
+  /**
+   * A fully-qualified stream wrapper class name to register for the test.
+   *
+   * @var string
+   */
   protected $classname = 'Drupal\file_test\DummyRemoteStreamWrapper';
 
   public static function getInfo() {
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedMoveTest.php b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedMoveTest.php
index 52a74fb..32d35ad 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedMoveTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedMoveTest.php
@@ -19,7 +19,18 @@ class RemoteFileUnmanagedMoveTest extends UnmanagedMoveTest {
    */
   public static $modules = array('file_test');
 
+  /**
+   * A stream wrapper scheme to register for the test.
+   *
+   * @var string
+   */
   protected $scheme = 'dummy-remote';
+
+  /**
+   * A fully-qualified stream wrapper class name to register for the test.
+   *
+   * @var string
+   */
   protected $classname = 'Drupal\file_test\DummyRemoteStreamWrapper';
 
   public static function getInfo() {
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedSaveDataTest.php b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedSaveDataTest.php
index 8dfd0e9..1e0b9ea 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedSaveDataTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/RemoteFileUnmanagedSaveDataTest.php
@@ -19,7 +19,18 @@ class RemoteFileUnmanagedSaveDataTest extends UnmanagedSaveDataTest {
    */
   public static $modules = array('file_test');
 
+  /**
+   * A stream wrapper scheme to register for the test.
+   *
+   * @var string
+   */
   protected $scheme = 'dummy-remote';
+
+  /**
+   * A fully-qualified stream wrapper class name to register for the test.
+   *
+   * @var string
+   */
   protected $classname = 'Drupal\file_test\DummyRemoteStreamWrapper';
 
   public static function getInfo() {
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/StreamWrapperTest.php b/core/modules/system/lib/Drupal/system/Tests/File/StreamWrapperTest.php
index e095ed4..35f85ab 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/StreamWrapperTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/StreamWrapperTest.php
@@ -21,7 +21,18 @@ class StreamWrapperTest extends FileTestBase {
    */
   public static $modules = array('file_test');
 
+  /**
+   * A stream wrapper scheme to register for the test.
+   *
+   * @var string
+   */
   protected $scheme = 'dummy';
+
+  /**
+   * A fully-qualified stream wrapper class name to register for the test.
+   *
+   * @var string
+   */
   protected $classname = 'Drupal\file_test\DummyStreamWrapper';
 
   public static function getInfo() {
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedSaveDataTest.php b/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedSaveDataTest.php
index 65755af..8590e52 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedSaveDataTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedSaveDataTest.php
@@ -37,6 +37,6 @@ function testFileSaveData() {
     $this->assertTrue($filepath, 'Unnamed file saved correctly.');
     $this->assertEqual('asdf.txt', drupal_basename($filepath), 'File was named correctly.');
     $this->assertEqual($contents, file_get_contents($filepath), 'Contents of the file are correct.');
-    $this->assertFilePermissions($filepath, 0777, 'file_chmod_file setting is respected.');
+    $this->assertFilePermissions($filepath, 0777);
   }
 }