Refine mapping equality test setup

Agent-Logs-Url: https://github.com/GalacticDynamics/xmmutablemap/sessions/f39253f1-d8ea-46eb-8a8e-f004866a473d

Co-authored-by: nstarman <8949649+nstarman@users.noreply.github.com>

Author: Copilot

tests/test_immutablemap.py

@@ -64,8 +64,9 @@ def test_hash(self, d: ImmutableMap[str, Any]) -> None:
         with pytest.raises(TypeError, match="unhashable type: 'set'"):
             hash(d)
 
-    def test_eq_with_other_mappings(self, d: ImmutableMap[str, Any]) -> None:
+    def test_eq_with_other_mappings(self) -> None:
         """Test mapping interoperability for `__eq__`."""
+        d = ImmutableMap(a=1, b=2)
         assert d == {"a": 1, "b": 2}
         assert d == OrderedDict([("a", 1), ("b", 2)])
         assert d == MappingProxyType({"a": 1, "b": 2})