TST: Add test for Timedelta hash invariance (#54035)

* Add test for timedelta hash equality inariance

* Ensure int bounds

* PR feedback

Author: harahu

pandas/tests/scalar/timedelta/test_timedelta.py

@@ -1,5 +1,6 @@
 """ test the scalar Timedelta """
 from datetime import timedelta
+import sys
 
 from hypothesis import (
     given,
@@ -918,6 +919,30 @@ def test_timedelta_hash_equality(self):
         ns_td = Timedelta(1, "ns")
         assert hash(ns_td) != hash(ns_td.to_pytimedelta())
 
+    @pytest.mark.xfail(
+        reason="pd.Timedelta violates the Python hash invariant (GH#44504).",
+        raises=AssertionError,
+    )
+    @given(
+        st.integers(
+            min_value=(-sys.maxsize - 1) // 500,
+            max_value=sys.maxsize // 500,
+        )
+    )
+    def test_hash_equality_invariance(self, half_microseconds: int) -> None:
+        # GH#44504
+
+        nanoseconds = half_microseconds * 500
+
+        pandas_timedelta = Timedelta(nanoseconds)
+        numpy_timedelta = np.timedelta64(nanoseconds)
+
+        # See: https://docs.python.org/3/glossary.html#term-hashable
+        # Hashable objects which compare equal must have the same hash value.
+        assert pandas_timedelta != numpy_timedelta or hash(pandas_timedelta) == hash(
+            numpy_timedelta
+        )
+
     def test_implementation_limits(self):
         min_td = Timedelta(Timedelta.min)
         max_td = Timedelta(Timedelta.max)