diff --git a/core/modules/system/lib/Drupal/system/Tests/Graph/GraphUnitTest.php b/core/modules/system/lib/Drupal/system/Tests/Graph/GraphUnitTest.php
index a68535c..0a64512 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Graph/GraphUnitTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Graph/GraphUnitTest.php
@@ -16,6 +16,7 @@
  * @see Drupal\Component\Graph\Graph
  */
 class GraphUnitTest extends UnitTestBase {
+
   public static function getInfo() {
     return array(
       'name' => 'Directed acyclic graph manipulation',
@@ -71,11 +72,12 @@ function testDepthFirstSearch() {
     );
     $this->assertReversePaths($graph, $expected_reverse_paths);
 
-    // Assert that DFS didn't created "missing" vertexes automatically.
-    $this->assertFALSE(isset($graph[6]), 'Vertex 6 has not been created');
+    // Assert target vertice 6 only has 'unlisted_sink'
+    $this->assertTRUE(isset($graph[6]), 'Vertex 6 has been created');
+    $this->assertTRUE(isset($graph[6]['unlisted_sink']), 'Vertex 6 is marked as unlisted_sink');
 
     $expected_components = array(
-      array(1, 2, 3, 4, 5, 7),
+      array(1, 2, 3, 4, 5, 6, 7),
       array(8, 9),
     );
     $this->assertComponents($graph, $expected_components);
@@ -90,6 +92,36 @@ function testDepthFirstSearch() {
     $this->assertWeights($graph, $expected_weights);
   }
 
+  function testGraphNormalized() {
+    $g = array();
+    // a -> b -> c
+    $g['a']['edges']['b'] = 1;
+    $g['b']['edges']['c'] = 1;
+
+    // disjunct f -> g
+    $g['f']['edges']['g'] = 1;
+
+    // disjunct p -> q
+    $g['p']['edges']['q'] = 1;
+
+    // A bypass a -> c
+    $g['a']['edges']['c'] = 1;
+
+    $graph_object = new Graph($g);
+    $sorted_graph = $graph_object->searchAndSort();
+
+    $this->assertTrue(isset($sorted_graph['c']), 'Vertice C is added to the GraphNormalized');
+
+    $tsl = $graph_object->getTopologicalSortedList();
+    $dummy = $tsl;
+
+    $head = array_shift($dummy);
+    $this->assertTrue(in_array($head, array('a', 'f', 'p')), "The TSL starts with a, f or p: " . join(', ', $tsl));
+
+    $tail = array_pop($dummy);
+    $this->assertTrue(in_array($tail, array('c', 'g', 'q')), "The TSL ends with c, g or q: " . join(', ', $tsl));
+  }
+
   /**
    * Return a normalized version of a graph.
    */
@@ -195,4 +227,5 @@ function displayArray($paths, $keys = FALSE) {
       return '(empty)';
     }
   }
+
 }