TST: xfail test for DatetimeIndex.union across DST boundary (GH#62915)

Author: antznette1

pandas/tests/indexes/datetimes/test_setops.py

@@ -60,6 +60,30 @@ def test_union3(self, sort, box):
         result = first.union(case, sort=sort)
         tm.assert_index_equal(result, expected)
 
+
+@pytest.mark.xfail(reason="see GH#62915: union across DST boundary", strict=False)
+def test_union_across_dst_boundary_xfail():
+    # US/Eastern DST spring-forward on 2021-03-14 at 02:00 (02:00-02:59 local time does not exist)
+    tz = "US/Eastern"
+    # Left side spans up to the missing hour window
+    left = date_range("2021-03-14 00:00", periods=3, freq="H", tz=tz)
+    # right side continues from the first valid post-DST hour
+    right = date_range("2021-03-14 03:00", periods=3, freq="H", tz=tz)
+
+    # Expect a union that preserves tz and includes valid hours without duplicates
+    expected = DatetimeIndex(
+        [
+            Timestamp("2021-03-14 00:00", tz=tz),
+            Timestamp("2021-03-14 01:00", tz=tz),
+            Timestamp("2021-03-14 03:00", tz=tz),
+            Timestamp("2021-03-14 04:00", tz=tz),
+            Timestamp("2021-03-14 05:00", tz=tz),
+        ]
+    )
+
+    result = left.union(right)
+    tm.assert_index_equal(result, expected)
+
     @pytest.mark.parametrize("tz", tz)
     def test_union(self, tz, sort):
         rng1 = date_range("1/1/2000", freq="D", periods=5, tz=tz)