fixed test as per comments

Author: ante012

pandas/tests/indexing/test_iloc.py

@@ -270,10 +270,15 @@ def test_iloc_setitem(self):
         tm.assert_series_equal(s, expected)
 
     @pytest.mark.parametrize(
-        "data, indexes, values, expected_k", [
-            ([[1, 22, 5], [1, 33, 6]], [0, -1, 1], [2, 3, 1], [7, 10]),
+        'data, indexes, values, expected_k', [
+            # test without indexer value in first level of MultiIndex
             ([[2, 22, 5], [2, 33, 6]], [0, -1, 1], [2, 3, 1], [7, 10]),
-            ([[1, 3, 7], [2, 4, 8]], [0, -1, 1], [1, 1, 10], [8, 19]),
+            # test like code sample 1 in the issue
+            ([[1, 22, 555], [1, 33, 666]], [0, -1, 1], [200, 300, 100],
+                [755, 1066]),
+            # test like code sample 2 in the issue
+            ([[1, 3, 7], [2, 4, 8]], [0, -1, 1], [10, 10, 1000], [17, 1018]),
+            # test like code sample 3 in the issue
             ([[1, 11, 4], [2, 22, 5], [3, 33, 6]], [0, -1, 1], [4, 7, 10],
                 [8, 15, 13])
         ])
@@ -283,14 +288,14 @@ def test_iloc_setitem_int_multiindex_series(
         df = pd.DataFrame(
             data=data,
             columns=['i', 'j', 'k'])
-        df.set_index(['i', 'j'], inplace=True)
+        df = df.set_index(['i', 'j'])
 
         series = df.k.copy()
         for i, v in zip(indexes, values):
             series.iloc[i] += v
 
-        df.k = expected_k
-        expected = df.k.copy()
+        df['k'] = expected_k
+        expected = df.k
         tm.assert_series_equal(series, expected)
 
     def test_iloc_setitem_list(self):