diff --git a/core/lib/Drupal/Component/Diff/DiffEngine.php b/core/lib/Drupal/Component/Diff/DiffEngine.php
index 0194379..fd6ce4b 100644
--- a/core/lib/Drupal/Component/Diff/DiffEngine.php
+++ b/core/lib/Drupal/Component/Diff/DiffEngine.php
@@ -8,6 +8,8 @@
  * You may copy this code freely under the conditions of the GPL.
  */
 
+namespace Drupal\Component\Diff;
+
 use Drupal\Component\Utility\Settings;
 use Drupal\Component\Utility\String;
 use Drupal\Component\Utility\Unicode;
@@ -570,7 +572,7 @@ function _shift_boundaries($lines, &$changed, $other_changed) {
  * @subpackage DifferenceEngine
  */
 class Diff {
-  var $edits;
+  public $edits;
 
   /**
    * Constructor.
@@ -580,7 +582,7 @@ class Diff {
    *      (Typically these are lines from a file.)
    * @param $to_lines array An array of strings.
    */
-  function Diff($from_lines, $to_lines) {
+  public function __construct($from_lines, $to_lines) {
     $eng = new _DiffEngine;
     $this->edits = $eng->diff($from_lines, $to_lines);
     //$this->_check($from_lines, $to_lines);
diff --git a/core/tests/Drupal/Tests/Component/Diff/DiffEngineTest.php b/core/tests/Drupal/Tests/Component/Diff/DiffEngineTest.php
index 97c1f57..91185e9 100644
--- a/core/tests/Drupal/Tests/Component/Diff/DiffEngineTest.php
+++ b/core/tests/Drupal/Tests/Component/Diff/DiffEngineTest.php
@@ -5,75 +5,83 @@
  * Contains \Drupal\Tests\Component\DiffEngineTest.
  */
 
-namespace Drupal\Tests\Component;
+namespace Drupal\Tests\Component\Diff;
 
+// Since this file holds more than a few classes, we can't rely on
+// autoloading the classes in its namespace.
+require_once(__DIR__ . '/../../../../../../core/lib/Drupal/Component/Diff/DiffEngine.php');
+
+use Drupal\Component\Diff\Diff;
+use Drupal\Component\Diff\_DiffOp_Copy;
+use Drupal\Component\Diff\_DiffOp_Add;
 use Drupal\Tests\UnitTestCase;
 
 /**
  * Tests the DiffEngine class.
+ *
+ * @group Drupal
+ * @group Component
+ * @group Diff
  */
 class DiffEngineTest extends UnitTestCase {
 
-    /**
-     * Lines array to use for testing.
-     *
-     * @var array
-     */
-    protected $lines1;
-
-    /**
-     * Lines array to use for testing.
-     *
-     * @var array
-     */
-    protected $lines2;
-
-    public static function getInfo() {
-        return array(
-            'name' => 'DiffEngine',
-            'description' => 'Tests the DiffEngine class.',
-            'group' => 'System',
-        );
-    }
-
-    function setUp() {
-        parent::setUp();
-
-        $this->lines1 = array(
-            'Hello World',
-            'I am an original line'
-        );
-
-        $this->lines2 = array(
-            'Hello World',
-            'I am a new line',
-            'I am an original line'
-        );
-    }
-
-    /**
-     * Tests Diff::Diff().
-     */
-    public function testDiff() {
-        define('DRUPAL_ROOT', __DIR__ .'/../../../../../../');
-        require_once DRUPAL_ROOT . '/core/lib/Drupal/Component/Diff/DiffEngine.php';
-
-        $diff = new \Diff($this->lines1, $this->lines2);
-
-        $expected = array(
-            new \_DiffOp_Copy(array('Hello World')),
-            new \_DiffOp_Add(array('I am a new line')),
-            new \_DiffOp_Copy(array('I am an original line'))
-        );
-
-        $this->assertCount(count($expected), $diff->edits);
-
-        foreach($diff->edits as $key => $diffObject) {
-            $this->assertInstanceOf(get_class($expected[$key]), $diffObject);
-            $this->assertSame($expected[$key]->orig, $diffObject->orig);
-            $this->assertSame($expected[$key]->closing, $diffObject->closing);
-        }
-
+  /**
+   * {@inheritdoc}
+   */
+  public static function getInfo() {
+    return array(
+      'name' => 'DiffEngine',
+      'description' => 'Tests the DiffEngine class.',
+      'group' => 'System',
+    );
+  }
+
+  /**
+   * Data provider for testDiff().
+   *
+   * @return
+   *  array Test data.
+   */
+  public function providerTestDiff() {
+    return array(
+      array(
+        // $expected
+        array(
+          new _DiffOp_Copy(array('Hello World')),
+          new _DiffOp_Add(array('I am a new line')),
+          new _DiffOp_Copy(array('I am an original line'))
+        ),
+        // $old
+        array(
+          'Hello World',
+          'I am an original line'
+        ),
+        // $new
+        array(
+          'Hello World',
+          'I am a new line',
+          'I am an original line'
+        ),
+      ),
+    );
+  }
+
+  /**
+   * Tests Diff::Diff().
+   *
+   * A basic test of the Diff class.
+   *
+   * @dataProvider providerTestDiff
+   */
+  public function testDiff($expected, $old, $new) {
+    $diff = new Diff($old, $new);
+    $this->assertCount(count($expected), $diff->edits);
+
+    foreach ($diff->edits as $key => $diffObject) {
+      $this->assertInstanceOf(get_class($expected[$key]), $diffObject);
+      $this->assertSame($expected[$key]->orig, $diffObject->orig);
+      $this->assertSame($expected[$key]->closing, $diffObject->closing);
     }
+  }
 
 }