add tests to Series/test_constructors; and update whatsnew

Author: BranYang

doc/source/whatsnew/v0.18.0.txt

@@ -796,3 +796,5 @@ Bug Fixes
 - Bug in ``.skew`` and ``.kurt`` due to roundoff error for highly similar values (:issue:`11974`)
 
 - Bug in ``buffer_rd_bytes`` src->buffer could be freed more than once if reading failed, causing a segfault (:issue:`12098`)
+
+- Bug in ``df.resample`` on categorical data with TimedeltaIndex (:issue:`12169`)

pandas/tests/series/test_constructors.py

@@ -519,6 +519,24 @@ def test_constructor_dict_multiindex(self):
         ser = ser.reindex(index=expected.index)
         check(ser, expected)
 
+    def test_constructor_dict_timedelta_index(self):
+        # GH #12169 : Resample category data with timedelta index
+        # construct Series from dict as data and TimedeltaIndex as index
+        # will result NaN in result Series data
+        expected = Series(
+            data=['A'] * 3,
+            index=pd.to_timedelta([0, 10, 20], unit='s')
+        )
+
+        result = Series(
+            data={pd.to_timedelta(0, unit='s'): 'A',
+                  pd.to_timedelta(10, unit='s'): 'A',
+                  pd.to_timedelta(20, unit='s'): 'A'},
+            index=pd.to_timedelta([0, 10, 20], unit='s')
+        )
+        # this should work
+        assert_series_equal(result, expected)
+
     def test_constructor_subclass_dict(self):
         data = tm.TestSubDict((x, 10.0 * x) for x in range(10))
         series = Series(data)