separate DatetimeIndex timezone tests

pandas/tests/indexes/datetimes/test_arithmetic.py

@@ -412,6 +412,14 @@ def test_dti_shift_no_freq(self):
         with pytest.raises(NullFrequencyError):
             dti.shift(2)
 
+    @pytest.mark.parametrize('tzstr', ['US/Eastern', 'dateutil/US/Eastern'])
+    def test_dti_shift_localized(self, tzstr):
+        dr = date_range('2011/1/1', '2012/1/1', freq='W-FRI')
+        dr_tz = dr.tz_localize(tzstr)
+
+        result = dr_tz.shift(1, '10T')
+        assert result.tz == dr_tz.tz
+
     # -------------------------------------------------------------
     # Binary operations DatetimeIndex and timedelta-like
 
@@ -767,6 +775,24 @@ def test_dti_with_offset_series(self, tz, names):
             res3 = dti - other
         tm.assert_series_equal(res3, expected_sub)
 
+    def test_dti_add_offset_tzaware(self):
+        dates = date_range('2012-11-01', periods=3, tz='US/Pacific')
+        offset = dates + pd.offsets.Hour(5)
+        assert dates[0] + pd.offsets.Hour(5) == offset[0]
+
+        # GH#6818
+        for tz in ['UTC', 'US/Pacific', 'Asia/Tokyo']:
+            dates = date_range('2010-11-01 00:00', periods=3, tz=tz, freq='H')
+            expected = DatetimeIndex(['2010-11-01 05:00', '2010-11-01 06:00',
+                                      '2010-11-01 07:00'], freq='H', tz=tz)
+
+            offset = dates + pd.offsets.Hour(5)
+            tm.assert_index_equal(offset, expected)
+            offset = dates + np.timedelta64(5, 'h')
+            tm.assert_index_equal(offset, expected)
+            offset = dates + timedelta(hours=5)
+            tm.assert_index_equal(offset, expected)
+
 
 @pytest.mark.parametrize('klass,assert_func', [
     (Series, tm.assert_series_equal),