.../lib/Drupal/system/Tests/File/DirectoryTest.php |   33 ++++++++++++++++++++
 .../lib/Drupal/system/Tests/File/FileTestBase.php  |    1 +
 2 files changed, 34 insertions(+)

diff --git a/core/modules/system/lib/Drupal/system/Tests/File/DirectoryTest.php b/core/modules/system/lib/Drupal/system/Tests/File/DirectoryTest.php
index 5d57bdf..a4db1ed 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/DirectoryTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/DirectoryTest.php
@@ -20,6 +20,39 @@ class DirectoryTest extends FileTestBase {
   }
 
   /**
+   * Test local directory handling functions.
+   */
+  function testFileCheckLocalDirectoryHandling() {
+    $directory = conf_path() . '/files';
+
+    // Check a new recursively created local directory for correct file system
+    // permissions.
+    $parent = $this->randomName();
+    $child = $this->randomName();
+
+    // Files directory already exists.
+    $this->assertTrue(is_dir($directory), t('Files directory already exists.'), 'File');
+    // Make files directory writable only.
+    $old_mode = fileperms($directory);
+
+    // Create the directories.
+    $parent_path = $directory . DIRECTORY_SEPARATOR . $parent;
+    $child_path = $parent_path . DIRECTORY_SEPARATOR . $child;
+    $this->assertTrue(drupal_mkdir($child_path, 0775, TRUE), t('No error reported when creating new local directories.'), 'File');
+
+    // Ensure new directories also exist.
+    $this->assertTrue(is_dir($parent_path), t('New parent directory actually exists.'), 'File');
+    $this->assertTrue(is_dir($child_path), t('New child directory actually exists.'), 'File');
+
+    // Check that new directory permissions were set properly.
+    $this->assertDirectoryPermissions($parent_path, 0775);
+    $this->assertDirectoryPermissions($child_path, 0775);
+
+    // Check that existing directory permissions were not modified.
+    $this->assertDirectoryPermissions($directory, $old_mode);
+  }
+
+  /**
    * Test directory handling functions.
    */
   function testFileCheckDirectoryHandling() {
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 90e62d7..5a59c49 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/FileTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/FileTestBase.php
@@ -121,6 +121,7 @@ abstract class FileTestBase extends WebTestBase {
 
     // Mask out all but the last three octets.
     $actual_mode = fileperms($directory) & 0777;
+    $expected_mode = $expected_mode & 0777;
 
     // PHP on Windows has limited support for file permissions. Usually each of
     // "user", "group" and "other" use one octal digit (3 bits) to represent the