TST: simplify tests for GH14346 (#14502)

Author: jorisvandenbossche

pandas/tests/indexes/test_datetimelike.py

@@ -732,30 +732,21 @@ def test_fillna_datetime64(self):
                            dtype=object)
             self.assert_index_equal(idx.fillna('x'), exp)
 
-    def test_difference_of_union(self):
-        # GH14323: Test taking the union of differences of an Index.
-        # Difference of DatetimeIndex does not preserve frequency,
-        # so a differencing operation should not retain the freq field of the
-        # original index.
-        i = pd.date_range("20160920", "20160925", freq="D")
-
-        a = pd.date_range("20160921", "20160924", freq="D")
-        expected = pd.DatetimeIndex(["20160920", "20160925"], freq=None)
-        a_diff = i.difference(a)
-        tm.assert_index_equal(a_diff, expected)
-        tm.assert_attr_equal('freq', a_diff, expected)
-
-        b = pd.date_range("20160922", "20160925", freq="D")
-        b_diff = i.difference(b)
-        expected = pd.DatetimeIndex(["20160920", "20160921"], freq=None)
-        tm.assert_index_equal(b_diff, expected)
-        tm.assert_attr_equal('freq', b_diff, expected)
-
-        union_of_diff = a_diff.union(b_diff)
-        expected = pd.DatetimeIndex(["20160920", "20160921", "20160925"],
-                                    freq=None)
-        tm.assert_index_equal(union_of_diff, expected)
-        tm.assert_attr_equal('freq', union_of_diff, expected)
+    def test_difference_freq(self):
+        # GH14323: difference of DatetimeIndex should not preserve frequency
+
+        index = date_range("20160920", "20160925", freq="D")
+        other = date_range("20160921", "20160924", freq="D")
+        expected = DatetimeIndex(["20160920", "20160925"], freq=None)
+        idx_diff = index.difference(other)
+        tm.assert_index_equal(idx_diff, expected)
+        tm.assert_attr_equal('freq', idx_diff, expected)
+
+        other = date_range("20160922", "20160925", freq="D")
+        idx_diff = index.difference(other)
+        expected = DatetimeIndex(["20160920", "20160921"], freq=None)
+        tm.assert_index_equal(idx_diff, expected)
+        tm.assert_attr_equal('freq', idx_diff, expected)
 
 
 class TestPeriodIndex(DatetimeLike, tm.TestCase):
@@ -963,29 +954,23 @@ def test_no_millisecond_field(self):
         with self.assertRaises(AttributeError):
             DatetimeIndex([]).millisecond
 
-    def test_difference_of_union(self):
-        # GH14323: Test taking the union of differences of an Index.
-        # Difference of Period MUST preserve frequency, but the ability
-        # to union results must be preserved
-        i = pd.period_range("20160920", "20160925", freq="D")
-
-        a = pd.period_range("20160921", "20160924", freq="D")
-        expected = pd.PeriodIndex(["20160920", "20160925"], freq='D')
-        a_diff = i.difference(a)
-        tm.assert_index_equal(a_diff, expected)
-        tm.assert_attr_equal('freq', a_diff, expected)
-
-        b = pd.period_range("20160922", "20160925", freq="D")
-        b_diff = i.difference(b)
-        expected = pd.PeriodIndex(["20160920", "20160921"], freq='D')
-        tm.assert_index_equal(b_diff, expected)
-        tm.assert_attr_equal('freq', b_diff, expected)
-
-        union_of_diff = a_diff.union(b_diff)
-        expected = pd.PeriodIndex(["20160920", "20160921", "20160925"],
-                                  freq='D')
-        tm.assert_index_equal(union_of_diff, expected)
-        tm.assert_attr_equal('freq', union_of_diff, expected)
+    def test_difference_freq(self):
+        # GH14323: difference of Period MUST preserve frequency
+        # but the ability to union results must be preserved
+
+        index = period_range("20160920", "20160925", freq="D")
+
+        other = period_range("20160921", "20160924", freq="D")
+        expected = PeriodIndex(["20160920", "20160925"], freq='D')
+        idx_diff = index.difference(other)
+        tm.assert_index_equal(idx_diff, expected)
+        tm.assert_attr_equal('freq', idx_diff, expected)
+
+        other = period_range("20160922", "20160925", freq="D")
+        idx_diff = index.difference(other)
+        expected = PeriodIndex(["20160920", "20160921"], freq='D')
+        tm.assert_index_equal(idx_diff, expected)
+        tm.assert_attr_equal('freq', idx_diff, expected)
 
 
 class TestTimedeltaIndex(DatetimeLike, tm.TestCase):
@@ -1199,27 +1184,19 @@ def test_fillna_timedelta(self):
             [pd.Timedelta('1 day'), 'x', pd.Timedelta('3 day')], dtype=object)
         self.assert_index_equal(idx.fillna('x'), exp)
 
-    def test_difference_of_union(self):
-        # GH14323: Test taking the union of differences of an Index.
-        # Difference of TimedeltaIndex does not preserve frequency,
-        # so a differencing operation should not retain the freq field of the
-        # original index.
-        i = pd.timedelta_range("0 days", "5 days", freq="D")
-
-        a = pd.timedelta_range("1 days", "4 days", freq="D")
-        expected = pd.TimedeltaIndex(["0 days", "5 days"], freq=None)
-        a_diff = i.difference(a)
-        tm.assert_index_equal(a_diff, expected)
-        tm.assert_attr_equal('freq', a_diff, expected)
-
-        b = pd.timedelta_range("2 days", "5 days", freq="D")
-        b_diff = i.difference(b)
-        expected = pd.TimedeltaIndex(["0 days", "1 days"], freq=None)
-        tm.assert_index_equal(b_diff, expected)
-        tm.assert_attr_equal('freq', b_diff, expected)
-
-        union_of_difference = a_diff.union(b_diff)
-        expected = pd.TimedeltaIndex(["0 days", "1 days", "5 days"],
-                                     freq=None)
-        tm.assert_index_equal(union_of_difference, expected)
-        tm.assert_attr_equal('freq', union_of_difference, expected)
+    def test_difference_freq(self):
+        # GH14323: Difference of TimedeltaIndex should not preserve frequency
+
+        index = timedelta_range("0 days", "5 days", freq="D")
+
+        other = timedelta_range("1 days", "4 days", freq="D")
+        expected = TimedeltaIndex(["0 days", "5 days"], freq=None)
+        idx_diff = index.difference(other)
+        tm.assert_index_equal(idx_diff, expected)
+        tm.assert_attr_equal('freq', idx_diff, expected)
+
+        other = timedelta_range("2 days", "5 days", freq="D")
+        idx_diff = index.difference(other)
+        expected = TimedeltaIndex(["0 days", "1 days"], freq=None)
+        tm.assert_index_equal(idx_diff, expected)
+        tm.assert_attr_equal('freq', idx_diff, expected)