diff --git a/src/zarr/testing/buffer.py b/src/zarr/testing/buffer.py
index 119ffc0a66..9d640d2c64 100644
--- a/src/zarr/testing/buffer.py
+++ b/src/zarr/testing/buffer.py
@@ -25,10 +25,14 @@
 class TestNDArrayLike(np.ndarray):
     """An example of a ndarray-like class"""
 
+    __test__ = False
+
 
 class TestBuffer(cpu.Buffer):
     """Example of a custom Buffer that handles ArrayLike"""
 
+    __test__ = False
+
 
 class NDBufferUsingTestNDArrayLike(cpu.NDBuffer):
     """Example of a custom NDBuffer that handles MyNDArrayLike"""
diff --git a/tests/v3/test_group.py b/tests/v3/test_group.py
index e588b6a11b..6989b406da 100644
--- a/tests/v3/test_group.py
+++ b/tests/v3/test_group.py
@@ -785,14 +785,15 @@ async def test_require_groups(store: LocalStore | MemoryStore, zarr_format: Zarr
 
 async def test_create_dataset(store: LocalStore | MemoryStore, zarr_format: ZarrFormat) -> None:
     root = await AsyncGroup.create(store=store, zarr_format=zarr_format)
-    foo = await root.create_dataset("foo", shape=(10,), dtype="uint8")
+    with pytest.warns(DeprecationWarning):
+        foo = await root.create_dataset("foo", shape=(10,), dtype="uint8")
     assert foo.shape == (10,)
 
-    with pytest.raises(ContainsArrayError):
+    with pytest.raises(ContainsArrayError), pytest.warns(DeprecationWarning):
         await root.create_dataset("foo", shape=(100,), dtype="int8")
 
     _ = await root.create_group("bar")
-    with pytest.raises(ContainsGroupError):
+    with pytest.raises(ContainsGroupError), pytest.warns(DeprecationWarning):
         await root.create_dataset("bar", shape=(100,), dtype="int8")