add some tests

Author: topper-123

pandas/tests/indexes/multi/test_compat.py

@@ -69,12 +69,16 @@ def test_inplace_mutation_resets_values():
     mi1 = MultiIndex(levels=levels, codes=codes)
     mi2 = MultiIndex(levels=levels2, codes=codes)
 
+    # instantiating MultiIndex should not access _values
     assert "_values" not in mi1._cache
     assert "_values" not in mi2._cache
 
     vals = mi1.values.copy()
     vals2 = mi2.values.copy()
 
+    # accessing .values should cache ._values
+    assert mi1._values is mi1._cache["_values"]
+    assert mi1.values is mi1._cache["_values"]
     assert isinstance(mi1._cache["_values"], np.ndarray)
 
     # Make sure level setting works