Requested changes

The changes involved:
- move test to pandas/tests/indexes/datetimes/test_datetime.py
- change try/except block to changing equality between expected and received result

Author: Mateusz Górski

pandas/tests/indexes/datetimes/test_datetime.py

@@ -457,3 +457,16 @@ def test_to_frame_datetime_tz(self):
         result = idx.to_frame()
         expected = DataFrame(idx, index=idx)
         tm.assert_frame_equal(result, expected)
+
+    def test_index_map(self):
+        # see GH20990
+        count = 6
+        index = pd.date_range("2018-01-01", periods=count, freq="M", name="name")
+        a = pd.Series(np.arange(count), index=index)
+        a.index = a.index.map(lambda x: (x.year, x.month))
+
+        df = pd.DataFrame([[2018, i + 1] for i in range(6)], columns=["name", "name"])
+        exp_index = pd.MultiIndex.from_frame(df)
+        expected = pd.Series(np.arange(count), index=exp_index)
+
+        tm.assert_series_equal(a, expected)

pandas/tests/series/indexing/test_indexing.py

@@ -907,18 +907,3 @@ def test_head_tail(test_data):
     assert_series_equal(test_data.series.head(0), test_data.series[0:0])
     assert_series_equal(test_data.series.tail(), test_data.series[-5:])
     assert_series_equal(test_data.series.tail(0), test_data.series[0:0])
-
-
-def test_index_map():
-    # see GH20990
-    count = 6
-    index = pd.date_range("2018-01-01", periods=count, freq="M")
-
-    a = Series(np.arange(count), index=index)
-    a.index.name = "name"
-
-    b = a.copy()
-    try:
-        b.index = a.index.map(lambda x: (x.year, x.month))
-    except ValueError:
-        pytest.fail("Unexpected ValueError")