diff --git a/core/modules/system/src/Tests/File/DirectoryTest.php b/core/modules/system/tests/src/Kernel/File/DirectoryTest.php
similarity index 98%
rename from core/modules/system/src/Tests/File/DirectoryTest.php
rename to core/modules/system/tests/src/Kernel/File/DirectoryTest.php
index 4c15a8e..90dcc80 100644
--- a/core/modules/system/src/Tests/File/DirectoryTest.php
+++ b/core/modules/system/tests/src/Kernel/File/DirectoryTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\DirectoryTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 use Drupal\Component\PhpStorage\FileStorage;
 
@@ -82,7 +82,7 @@ function testFileCheckDirectoryHandling() {
       $this->assertFalse(file_prepare_directory($directory, 0), 'Error reported for a non-writeable directory.', 'File');
 
       // Test directory permission modification.
-      $this->settingsSet('file_chmod_directory', 0777);
+      $this->setSetting('file_chmod_directory', 0777);
       $this->assertTrue(file_prepare_directory($directory, FILE_MODIFY_PERMISSIONS), 'No error reported when making directory writeable.', 'File');
     }
 
diff --git a/core/modules/system/src/Tests/File/FileTestBase.php b/core/modules/system/tests/src/Kernel/File/FileTestBase.php
similarity index 92%
rename from core/modules/system/src/Tests/File/FileTestBase.php
rename to core/modules/system/tests/src/Kernel/File/FileTestBase.php
index 93e998d..dccbef2 100644
--- a/core/modules/system/src/Tests/File/FileTestBase.php
+++ b/core/modules/system/tests/src/Kernel/File/FileTestBase.php
@@ -5,9 +5,10 @@
  * Contains \Drupal\system\Tests\File\FileTestBase.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
-use Drupal\simpletest\KernelTestBase;
+use Drupal\Core\StreamWrapper\StreamWrapperInterface;
+use Drupal\KernelTests\KernelTestBase;
 
 /**
  * Base class for file tests that adds some additional file specific
@@ -39,10 +40,10 @@
   protected function setUp() {
     parent::setUp();
     $this->installConfig(array('system'));
-    $this->registerStreamWrapper('private', 'Drupal\Core\StreamWrapper\PrivateStream');
+    $this->container->get('stream_wrapper_manager')->registerWrapper('private', 'Drupal\Core\StreamWrapper\PrivateStream', StreamWrapperInterface::NORMAL);
 
     if (isset($this->scheme)) {
-      $this->registerStreamWrapper($this->scheme, $this->classname);
+      $this->container->get('stream_wrapper_manager')->registerWrapper($this->scheme, $this->classname, StreamWrapperInterface::NORMAL);
     }
   }
 
diff --git a/core/modules/system/src/Tests/File/MimeTypeTest.php b/core/modules/system/tests/src/Kernel/File/MimeTypeTest.php
similarity index 98%
rename from core/modules/system/src/Tests/File/MimeTypeTest.php
rename to core/modules/system/tests/src/Kernel/File/MimeTypeTest.php
index 6324bf0..8e217b8 100644
--- a/core/modules/system/src/Tests/File/MimeTypeTest.php
+++ b/core/modules/system/tests/src/Kernel/File/MimeTypeTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\MimeTypeTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests filename mimetype detection.
diff --git a/core/modules/system/src/Tests/File/NameMungingTest.php b/core/modules/system/tests/src/Kernel/File/NameMungingTest.php
similarity index 98%
rename from core/modules/system/src/Tests/File/NameMungingTest.php
rename to core/modules/system/tests/src/Kernel/File/NameMungingTest.php
index 3afd273..cbda7b3 100644
--- a/core/modules/system/src/Tests/File/NameMungingTest.php
+++ b/core/modules/system/tests/src/Kernel/File/NameMungingTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\NameMungingTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests filename munging and unmunging.
diff --git a/core/modules/system/src/Tests/File/ReadOnlyStreamWrapperTest.php b/core/modules/system/tests/src/Kernel/File/ReadOnlyStreamWrapperTest.php
similarity index 99%
rename from core/modules/system/src/Tests/File/ReadOnlyStreamWrapperTest.php
rename to core/modules/system/tests/src/Kernel/File/ReadOnlyStreamWrapperTest.php
index 4e43d3e..d2403b3 100644
--- a/core/modules/system/src/Tests/File/ReadOnlyStreamWrapperTest.php
+++ b/core/modules/system/tests/src/Kernel/File/ReadOnlyStreamWrapperTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\ReadOnlyStreamWrapperTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests the read-only stream wrapper write functions.
diff --git a/core/modules/system/src/Tests/File/RemoteFileDirectoryTest.php b/core/modules/system/tests/src/Kernel/File/RemoteFileDirectoryTest.php
similarity index 94%
rename from core/modules/system/src/Tests/File/RemoteFileDirectoryTest.php
rename to core/modules/system/tests/src/Kernel/File/RemoteFileDirectoryTest.php
index 12e3267..6b43b2d 100644
--- a/core/modules/system/src/Tests/File/RemoteFileDirectoryTest.php
+++ b/core/modules/system/tests/src/Kernel/File/RemoteFileDirectoryTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\RemoteFileDirectoryTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests operations dealing with directories.
diff --git a/core/modules/system/src/Tests/File/RemoteFileScanDirectoryTest.php b/core/modules/system/tests/src/Kernel/File/RemoteFileScanDirectoryTest.php
similarity index 94%
rename from core/modules/system/src/Tests/File/RemoteFileScanDirectoryTest.php
rename to core/modules/system/tests/src/Kernel/File/RemoteFileScanDirectoryTest.php
index 4f601f8..688764b 100644
--- a/core/modules/system/src/Tests/File/RemoteFileScanDirectoryTest.php
+++ b/core/modules/system/tests/src/Kernel/File/RemoteFileScanDirectoryTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\RemoteFileScanDirectoryTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests the file_scan_directory() function.
diff --git a/core/modules/system/src/Tests/File/RemoteFileUnmanagedCopyTest.php b/core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedCopyTest.php
similarity index 94%
rename from core/modules/system/src/Tests/File/RemoteFileUnmanagedCopyTest.php
rename to core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedCopyTest.php
index bf2a518..bb34e6f 100644
--- a/core/modules/system/src/Tests/File/RemoteFileUnmanagedCopyTest.php
+++ b/core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedCopyTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\RemoteFileUnmanagedCopyTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests the unmanaged file copy function.
diff --git a/core/modules/system/src/Tests/File/RemoteFileUnmanagedDeleteRecursiveTest.php b/core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedDeleteRecursiveTest.php
similarity index 95%
rename from core/modules/system/src/Tests/File/RemoteFileUnmanagedDeleteRecursiveTest.php
rename to core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedDeleteRecursiveTest.php
index 0eb8c2f..3bf86da 100644
--- a/core/modules/system/src/Tests/File/RemoteFileUnmanagedDeleteRecursiveTest.php
+++ b/core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedDeleteRecursiveTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\RemoteFileUnmanagedDeleteRecursiveTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests the unmanaged file delete recursive function.
diff --git a/core/modules/system/src/Tests/File/RemoteFileUnmanagedDeleteTest.php b/core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedDeleteTest.php
similarity index 94%
rename from core/modules/system/src/Tests/File/RemoteFileUnmanagedDeleteTest.php
rename to core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedDeleteTest.php
index 0fc0368..78e99dc 100644
--- a/core/modules/system/src/Tests/File/RemoteFileUnmanagedDeleteTest.php
+++ b/core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedDeleteTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\RemoteFileUnmanagedDeleteTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests the unmanaged file delete function.
diff --git a/core/modules/system/src/Tests/File/RemoteFileUnmanagedMoveTest.php b/core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedMoveTest.php
similarity index 94%
rename from core/modules/system/src/Tests/File/RemoteFileUnmanagedMoveTest.php
rename to core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedMoveTest.php
index 41e2f6c..170ffb1 100644
--- a/core/modules/system/src/Tests/File/RemoteFileUnmanagedMoveTest.php
+++ b/core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedMoveTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\RemoteFileUnmanagedMoveTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests the unmanaged file move function.
diff --git a/core/modules/system/src/Tests/File/RemoteFileUnmanagedSaveDataTest.php b/core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedSaveDataTest.php
similarity index 94%
rename from core/modules/system/src/Tests/File/RemoteFileUnmanagedSaveDataTest.php
rename to core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedSaveDataTest.php
index 4c43330..8ad87ff 100644
--- a/core/modules/system/src/Tests/File/RemoteFileUnmanagedSaveDataTest.php
+++ b/core/modules/system/tests/src/Kernel/File/RemoteFileUnmanagedSaveDataTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\RemoteFileUnmanagedSaveDataTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests the unmanaged file save data function.
diff --git a/core/modules/system/src/Tests/File/ScanDirectoryTest.php b/core/modules/system/tests/src/Kernel/File/ScanDirectoryTest.php
similarity index 99%
rename from core/modules/system/src/Tests/File/ScanDirectoryTest.php
rename to core/modules/system/tests/src/Kernel/File/ScanDirectoryTest.php
index 4b067f0..3ac512e 100644
--- a/core/modules/system/src/Tests/File/ScanDirectoryTest.php
+++ b/core/modules/system/tests/src/Kernel/File/ScanDirectoryTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\ScanDirectoryTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests the file_scan_directory() function.
diff --git a/core/modules/system/src/Tests/File/StreamWrapperTest.php b/core/modules/system/tests/src/Kernel/File/StreamWrapperTest.php
similarity index 97%
rename from core/modules/system/src/Tests/File/StreamWrapperTest.php
rename to core/modules/system/tests/src/Kernel/File/StreamWrapperTest.php
index 5816861..16e4e25 100644
--- a/core/modules/system/src/Tests/File/StreamWrapperTest.php
+++ b/core/modules/system/tests/src/Kernel/File/StreamWrapperTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\StreamWrapperTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 use Drupal\Core\DrupalKernel;
 use Drupal\Core\Site\Settings;
@@ -41,14 +41,12 @@ class StreamWrapperTest extends FileTestBase {
   protected $classname = 'Drupal\file_test\StreamWrapper\DummyStreamWrapper';
 
   function setUp() {
+    parent::setUp();
+
     // Add file_private_path setting.
-    $settings = Settings::getAll();
     $request = Request::create('/');;
     $site_path = DrupalKernel::findSitePath($request);
-    $settings['file_private_path'] = $site_path . '/private';
-    new Settings($settings + Settings::getAll());
-
-    parent::setUp();
+    $this->setSetting('file_private_path', $site_path . '/private');
   }
 
   /**
diff --git a/core/modules/system/src/Tests/File/UnmanagedCopyTest.php b/core/modules/system/tests/src/Kernel/File/UnmanagedCopyTest.php
similarity index 98%
rename from core/modules/system/src/Tests/File/UnmanagedCopyTest.php
rename to core/modules/system/tests/src/Kernel/File/UnmanagedCopyTest.php
index 22a0615..ae36584 100644
--- a/core/modules/system/src/Tests/File/UnmanagedCopyTest.php
+++ b/core/modules/system/tests/src/Kernel/File/UnmanagedCopyTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\UnmanagedCopyTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 use Drupal\Core\Site\Settings;
 use Drupal\Core\File\FileSystem;
diff --git a/core/modules/system/src/Tests/File/UnmanagedDeleteRecursiveTest.php b/core/modules/system/tests/src/Kernel/File/UnmanagedDeleteRecursiveTest.php
similarity index 98%
rename from core/modules/system/src/Tests/File/UnmanagedDeleteRecursiveTest.php
rename to core/modules/system/tests/src/Kernel/File/UnmanagedDeleteRecursiveTest.php
index abef365..463df24 100644
--- a/core/modules/system/src/Tests/File/UnmanagedDeleteRecursiveTest.php
+++ b/core/modules/system/tests/src/Kernel/File/UnmanagedDeleteRecursiveTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\UnmanagedDeleteRecursiveTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests the unmanaged file delete recursive function.
diff --git a/core/modules/system/src/Tests/File/UnmanagedDeleteTest.php b/core/modules/system/tests/src/Kernel/File/UnmanagedDeleteTest.php
similarity index 96%
rename from core/modules/system/src/Tests/File/UnmanagedDeleteTest.php
rename to core/modules/system/tests/src/Kernel/File/UnmanagedDeleteTest.php
index 5cdcfe8..7784485 100644
--- a/core/modules/system/src/Tests/File/UnmanagedDeleteTest.php
+++ b/core/modules/system/tests/src/Kernel/File/UnmanagedDeleteTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\UnmanagedDeleteTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests the unmanaged file delete function.
diff --git a/core/modules/system/src/Tests/File/UnmanagedMoveTest.php b/core/modules/system/tests/src/Kernel/File/UnmanagedMoveTest.php
similarity index 98%
rename from core/modules/system/src/Tests/File/UnmanagedMoveTest.php
rename to core/modules/system/tests/src/Kernel/File/UnmanagedMoveTest.php
index 4a4e9e9..d3843a7 100644
--- a/core/modules/system/src/Tests/File/UnmanagedMoveTest.php
+++ b/core/modules/system/tests/src/Kernel/File/UnmanagedMoveTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\UnmanagedMoveTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 use Drupal\Core\Site\Settings;
 use Drupal\Core\File\FileSystem;
diff --git a/core/modules/system/src/Tests/File/UnmanagedSaveDataTest.php b/core/modules/system/tests/src/Kernel/File/UnmanagedSaveDataTest.php
similarity index 92%
rename from core/modules/system/src/Tests/File/UnmanagedSaveDataTest.php
rename to core/modules/system/tests/src/Kernel/File/UnmanagedSaveDataTest.php
index 2d3342c..9c460a3 100644
--- a/core/modules/system/src/Tests/File/UnmanagedSaveDataTest.php
+++ b/core/modules/system/tests/src/Kernel/File/UnmanagedSaveDataTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\UnmanagedSaveDataTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 /**
  * Tests the file_unmanaged_save_data() function.
@@ -18,7 +18,7 @@ class UnmanagedSaveDataTest extends FileTestBase {
    */
   function testFileSaveData() {
     $contents = $this->randomMachineName(8);
-    $this->settingsSet('file_chmod_file', 0777);
+    $this->setSetting('file_chmod_file', 0777);
 
     // No filename.
     $filepath = file_unmanaged_save_data($contents);
diff --git a/core/modules/system/src/Tests/File/UrlRewritingTest.php b/core/modules/system/tests/src/Kernel/File/UrlRewritingTest.php
similarity index 99%
rename from core/modules/system/src/Tests/File/UrlRewritingTest.php
rename to core/modules/system/tests/src/Kernel/File/UrlRewritingTest.php
index dd37222..2bd9eda 100644
--- a/core/modules/system/src/Tests/File/UrlRewritingTest.php
+++ b/core/modules/system/tests/src/Kernel/File/UrlRewritingTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\system\Tests\File\UrlRewritingTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\Tests\system\Kernel\File;
 
 use Symfony\Component\HttpFoundation\Request;
 
diff --git a/core/modules/system/src/Tests/File/HtaccessUnitTest.php b/core/tests/Drupal/KernelTests/Core/File/HtaccessUnitTest.php
similarity index 93%
rename from core/modules/system/src/Tests/File/HtaccessUnitTest.php
rename to core/tests/Drupal/KernelTests/Core/File/HtaccessUnitTest.php
index 4b7f39d..490f967 100644
--- a/core/modules/system/src/Tests/File/HtaccessUnitTest.php
+++ b/core/tests/Drupal/KernelTests/Core/File/HtaccessUnitTest.php
@@ -5,10 +5,11 @@
  * Contains \Drupal\system\Tests\File\HtaccessUnitTest.
  */
 
-namespace Drupal\system\Tests\File;
+namespace Drupal\KernelTests\Core\File;
 
 use Drupal\Component\Utility\SafeMarkup;
-use Drupal\simpletest\KernelTestBase;
+use Drupal\Core\Site\Settings;
+use Drupal\KernelTests\KernelTestBase;
 
 /**
  * Tests .htaccess file saving.
@@ -22,8 +23,8 @@ class HtaccessUnitTest extends KernelTestBase {
    */
   function testHtaccessSave() {
     // Prepare test directories.
-    $public = $this->publicFilesDirectory . '/test/public';
-    $private = $this->publicFilesDirectory . '/test/private';
+    $public = Settings::get('file_public_path') . '/test/public';
+    $private = Settings::get('file_public_path') . '/test/private';
     $stream = 'public://test/stream';
 
     // Verify that file_save_htaccess() returns FALSE if .htaccess cannot be