diff --git a/xarray/backends/zarr.py b/xarray/backends/zarr.py
index c06bdecebb6..56403d76114 100644
--- a/xarray/backends/zarr.py
+++ b/xarray/backends/zarr.py
@@ -666,7 +666,7 @@ def open_store(
                 write_empty,
                 close_store_on_close,
                 use_zarr_fill_value_as_mask,
-                cache_members=cache_members
+                cache_members=cache_members,
             )
             for group in group_paths
         }
@@ -774,16 +774,18 @@ def _fetch_members(self) -> dict[str, ZarrArray]:
     def _update_members(self, data: dict[str, ZarrArray]):
         if not self._cache_members:
             msg = (
-                'Updating the members cache is only valid if this object was created '
-                'with cache_members=True, but this object has `cache_members=False`.' 
-                f'You should update the zarr group directly.'
-                )
+                "Updating the members cache is only valid if this object was created "
+                "with cache_members=True, but this object has `cache_members=False`."
+                "You should update the zarr group directly."
+            )
             raise ValueError(msg)
         else:
             self._members = {**self.members, **data}
 
     def array_keys(self) -> tuple[str, ...]:
-        return tuple(key for (key, node) in self.members.items() if isinstance(node, ZarrArray))
+        return tuple(
+            key for (key, node) in self.members.items() if isinstance(node, ZarrArray)
+        )
 
     def arrays(self) -> tuple[tuple[str, ZarrArray], ...]:
         return tuple(
diff --git a/xarray/tests/test_backends.py b/xarray/tests/test_backends.py
index 14756c19bb0..b638aa70905 100644
--- a/xarray/tests/test_backends.py
+++ b/xarray/tests/test_backends.py
@@ -2278,7 +2278,10 @@ def create_zarr_target(self):
     def create_store(self, cache_members: bool = True):
         with self.create_zarr_target() as store_target:
             yield backends.ZarrStore.open_group(
-                store_target, mode="w", cache_members=cache_members, **self.version_kwargs
+                store_target,
+                mode="w",
+                cache_members=cache_members,
+                **self.version_kwargs,
             )
 
     def save(self, dataset, store_target, **kwargs):  # type: ignore[override]
@@ -2594,7 +2597,7 @@ def test_hidden_zarr_keys(self) -> None:
 
             # put it back and try removing from a variable
             del zarr_group["var2"].attrs[self.DIMENSION_KEY]
-            
+
             with pytest.raises(KeyError):
                 with xr.decode_cf(store):
                     pass
@@ -3262,10 +3265,10 @@ def test_chunked_cftime_datetime(self) -> None:
     def test_cache_members(self) -> None:
         """
         Ensure that if `ZarrStore` is created with `cache_members` set to `True`,
-        a `ZarrStore` only inspects the underlying zarr group once, 
+        a `ZarrStore` only inspects the underlying zarr group once,
         and that the results of that inspection are cached.
 
-        Otherwise, `ZarrStore.members` should inspect the underlying zarr group each time it is 
+        Otherwise, `ZarrStore.members` should inspect the underlying zarr group each time it is
         invoked
         """
         with self.create_zarr_target() as store_target:
@@ -3290,16 +3293,14 @@ def test_cache_members(self) -> None:
             # create a new array
             new_key = "baz"
             zstore_mut.zarr_group.create(name=new_key, shape=(1,), dtype="uint8")
-            
+
             observed_keys_1 = sorted(zstore_stat.array_keys())
             assert observed_keys_1 == array_keys
-            
+
             observed_keys_2 = sorted(zstore_mut.array_keys())
             assert observed_keys_2 == sorted(array_keys + [new_key])
 
 
-
-
 @requires_zarr
 @pytest.mark.skipif(
     KVStore is None, reason="zarr-python 2.x or ZARR_V3_EXPERIMENTAL_API is unset."
@@ -3564,7 +3565,9 @@ def create_zarr_target(self):
     @contextlib.contextmanager
     def create_store(self, cache_members: bool = True):
         with self.create_zarr_target() as store_target:
-            group = backends.ZarrStore.open_group(store_target, mode="a", cache_members=cache_members)
+            group = backends.ZarrStore.open_group(
+                store_target, mode="a", cache_members=cache_members
+            )
             yield group