TST: Apply method broken for empty integer series with datetime index (pandas-dev#29358)

Author: okz12

pandas/tests/series/test_apply.py

@@ -170,6 +170,12 @@ def test_apply_categorical_with_nan_values(self, series):
         expected = expected.astype(object)
         tm.assert_series_equal(result, expected)
 
+    def test_apply_empty_integer_series_with_datetime_index(self):
+        # GH 21245
+        s = pd.Series([], index=pd.date_range(start="2018-01-01", periods=0), dtype=int)
+        result = s.apply(lambda x: x)
+        tm.assert_series_equal(result, s)
+
 
 class TestSeriesAggregate:
     def test_transform(self, string_series):