use second roundtrip to test for dtype

Author: kmuehlbauer

xarray/tests/test_backends.py

@@ -632,7 +632,9 @@ def test_roundtrip_boolean_dtype(self) -> None:
         with self.roundtrip(original) as actual:
             assert_identical(original, actual)
             assert actual["x"].dtype == "bool"
-            assert actual["x"].encoding["dtype"] == "bool"
+            with self.roundtrip(actual) as actual2:
+                assert_identical(original, actual2)
+                assert actual2["x"].dtype == "bool"
 
     def test_orthogonal_indexing(self) -> None:
         in_memory = create_test_data()