Fix typing issues in tests (#8312)

* Fix typing issues in tests

* Update test_variable.py

Author: Illviljan

xarray/tests/test_indexing.py

@@ -307,6 +307,7 @@ def test_lazily_indexed_array(self) -> None:
                         assert expected.shape == actual.shape
                         assert_array_equal(expected, actual)
                         assert isinstance(actual._data, indexing.LazilyIndexedArray)
+                        assert isinstance(v_lazy._data, indexing.LazilyIndexedArray)
 
                         # make sure actual.key is appropriate type
                         if all(

xarray/tests/test_variable.py

@@ -2945,6 +2945,7 @@ def test_datetime_conversion_warning(values, warns_under_pandas_version_two) ->
         # The only case where a non-datetime64 dtype can occur currently is in
         # the case that the variable is backed by a timezone-aware
         # DatetimeIndex, and thus is hidden within the PandasIndexingAdapter class.
+        assert isinstance(var._data, PandasIndexingAdapter)
         assert var._data.array.dtype == pd.DatetimeTZDtype(
             "ns", pytz.timezone("America/New_York")
         )
@@ -2978,6 +2979,7 @@ def test_pandas_two_only_datetime_conversion_warnings() -> None:
         # The only case where a non-datetime64 dtype can occur currently is in
         # the case that the variable is backed by a timezone-aware
         # DatetimeIndex, and thus is hidden within the PandasIndexingAdapter class.
+        assert isinstance(var._data, PandasIndexingAdapter)
         assert var._data.array.dtype == pd.DatetimeTZDtype(
             "ns", pytz.timezone("America/New_York")
         )