diff --git a/core/modules/system/src/Tests/Common/ExtensionDiscoveryProfilesTest.php b/core/modules/system/src/Tests/Common/ExtensionDiscoveryProfilesTest.php
new file mode 100644
index 0000000..4ae1713
--- /dev/null
+++ b/core/modules/system/src/Tests/Common/ExtensionDiscoveryProfilesTest.php
@@ -0,0 +1,65 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Common\ExtensionDiscoveryProfilesTest.
+ */
+
+namespace Drupal\system\Tests\Common;
+
+use Drupal\Core\Extension\ExtensionDiscovery;
+use Drupal\Core\Site\Settings;
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Tests setting profileDirectories from settings.
+ *
+ * @group Common
+ */
+class ExtensionDiscoveryProfilesTest extends KernelTestBase {
+  /**
+   * Tests that files in different directories take precedence as expected.
+   */
+  function testDirectoryPrecedence() {
+    // Define the module files we will search for, and the directory precedence
+    // we expect.
+    $expected_directories = array(
+      // When both copies of the module are compatible with Drupal core, the
+      // copy in the profile directory takes precedence.
+      'drupal_system_listing_compatible_test' => array(
+        'core/profiles/testing/modules',
+        'core/modules/system/tests/modules',
+      ),
+    );
+
+    // This test relies on two versions of the same module existing in
+    // different places in the filesystem. Without that, the test has no
+    // meaning, so assert their presence first.
+    foreach ($expected_directories as $module => $directories) {
+      foreach ($directories as $directory) {
+        $filename = "$directory/$module/$module.info.yml";
+        $this->assertTrue(file_exists(\Drupal::root() . '/' . $filename), format_string('@filename exists.', array('@filename' => $filename)));
+      }
+    }
+
+    // Now add the testing profile path to settings.
+    $settings = Settings::getAll();
+    $settings['profile_directories'] = array (
+      0 => 'core/profiles/testing',
+    );
+    new Settings($settings);
+
+    // Now scan the directories and check that the files take precedence as
+    // expected.
+    $listing = new ExtensionDiscovery(\Drupal::root());
+    $files = $listing->scan('module');
+    foreach ($expected_directories as $module => $directories) {
+      $expected_directory = array_shift($directories);
+      $expected_uri = "$expected_directory/$module/$module.info.yml";
+      $this->assertEqual($files[$module]->getPathname(), $expected_uri, format_string('Module @actual was found at @expected.', array(
+        '@actual' => $files[$module]->getPathname(),
+        '@expected' => $expected_uri,
+      )));
+    }
+  }
+}