diff --git a/sorting_searching/quick_sort/quick_sort_challenge.ipynb b/sorting_searching/quick_sort/quick_sort_challenge.ipynb
index 65e04c9..5f9d6eb 100644
--- a/sorting_searching/quick_sort/quick_sort_challenge.ipynb
+++ b/sorting_searching/quick_sort/quick_sort_challenge.ipynb
@@ -105,18 +105,18 @@
     "    def test_quick_sort(self, func):\n",
     "        print('Empty input')\n",
     "        data = []\n",
-    "        func(data)\n",
-    "        assert_equal(data, [])\n",
+    "        sorted_data = func(data)\n",
+    "        assert_equal(sorted_data, [])\n",
     "\n",
     "        print('One element')\n",
     "        data = [5]\n",
-    "        func(data)\n",
-    "        assert_equal(data, [5])\n",
+    "        sorted_data = func(data)\n",
+    "        assert_equal(sorted_data, [5])\n",
     "\n",
     "        print('Two or more elements')\n",
     "        data = [5, 1, 7, 2, 6, -3, 5, 7, -1]\n",
-    "        data = func(data)\n",
-    "        assert_equal(data, sorted(data))\n",
+    "        sorted_data = func(data)\n",
+    "        assert_equal(sorted_data, sorted(data))\n",
     "\n",
     "        print('Success: test_quick_sort\\n')\n",
     "\n",
diff --git a/sorting_searching/quick_sort/quick_sort_solution.ipynb b/sorting_searching/quick_sort/quick_sort_solution.ipynb
index e06db1f..8e0d8f8 100644
--- a/sorting_searching/quick_sort/quick_sort_solution.ipynb
+++ b/sorting_searching/quick_sort/quick_sort_solution.ipynb
@@ -169,18 +169,18 @@
     "    def test_quick_sort(self, func):\n",
     "        print('Empty input')\n",
     "        data = []\n",
-    "        func(data)\n",
-    "        assert_equal(data, [])\n",
+    "        sorted_data = func(data)\n",
+    "        assert_equal(sorted_data, [])\n",
     "\n",
     "        print('One element')\n",
     "        data = [5]\n",
-    "        func(data)\n",
-    "        assert_equal(data, [5])\n",
+    "        sorted_data = func(data)\n",
+    "        assert_equal(sorted_data, [5])\n",
     "\n",
     "        print('Two or more elements')\n",
     "        data = [5, 1, 7, 2, 6, -3, 5, 7, -1]\n",
-    "        data = func(data)\n",
-    "        assert_equal(data, sorted(data))\n",
+    "        sorted_data = func(data)\n",
+    "        assert_equal(sorted_data, sorted(data))\n",
     "\n",
     "        print('Success: test_quick_sort\\n')\n",
     "\n",
diff --git a/sorting_searching/quick_sort/test_quick_sort.py b/sorting_searching/quick_sort/test_quick_sort.py
index 3da236d..691a75a 100644
--- a/sorting_searching/quick_sort/test_quick_sort.py
+++ b/sorting_searching/quick_sort/test_quick_sort.py
@@ -5,18 +5,18 @@ class TestQuickSort(object):
     def test_quick_sort(self, func):
         print('Empty input')
         data = []
-        func(data)
-        assert_equal(data, [])
+        sorted_data = func(data)
+        assert_equal(sorted_data, [])
 
         print('One element')
         data = [5]
-        func(data)
-        assert_equal(data, [5])
+        sorted_data = func(data)
+        assert_equal(sorted_data, [5])
 
         print('Two or more elements')
         data = [5, 1, 7, 2, 6, -3, 5, 7, -1]
-        data = func(data)
-        assert_equal(data, sorted(data))
+        sorted_data = func(data)
+        assert_equal(sorted_data, sorted(data))
 
         print('Success: test_quick_sort\n')