diff --git a/distributed_shampoo/tests/shampoo_types_test.py b/distributed_shampoo/tests/shampoo_types_test.py
index 4e2e3cb..2fbebbb 100644
--- a/distributed_shampoo/tests/shampoo_types_test.py
+++ b/distributed_shampoo/tests/shampoo_types_test.py
@@ -24,21 +24,37 @@
 SubclassesType = TypeVar("SubclassesType")
 
 
-def get_all_subclasses(cls: SubclassesType) -> list[SubclassesType]:
+def get_all_subclasses(
+    cls: SubclassesType, include_cls_self: bool = True
+) -> list[SubclassesType]:
+    """
+    Retrieves all subclasses of a given class, optionally including the class itself.
+
+    This function uses a helper function to recursively find all unique subclasses
+    of the specified class.
+
+    Args:
+        cls (SubclassesType): The class for which to find subclasses.
+        include_cls_self (bool): Whether to include the class itself in the result. (Default: True)
+
+    Returns:
+        list[SubclassesType]: A list of all unique subclasses of the given class.
+    """
+
     def get_all_unique_subclasses(cls: SubclassesType) -> set[SubclassesType]:
         """Gets all unique subclasses of a given class recursively."""
         assert (
             subclasses := getattr(cls, "__subclasses__", lambda: None)()
         ) is not None, f"{cls} does not have __subclasses__."
-        return reduce(or_, map(get_all_unique_subclasses, subclasses), set())
+        return reduce(or_, map(get_all_unique_subclasses, subclasses), {cls})
 
-    return list(get_all_unique_subclasses(cls))
+    return list(get_all_unique_subclasses(cls) - (set() if include_cls_self else {cls}))
 
 
 class AdaGradGraftingConfigSubclassesTest(unittest.TestCase):
     def test_illegal_epsilon(self) -> None:
         epsilon = 0.0
-        for cls in [AdaGradGraftingConfig] + get_all_subclasses(AdaGradGraftingConfig):
+        for cls in get_all_subclasses(AdaGradGraftingConfig):
             with self.subTest(cls=cls):
                 self.assertRaisesRegex(
                     ValueError,
@@ -53,7 +69,7 @@ def test_illegal_beta2(
         self,
     ) -> None:
         for cls, beta2 in itertools.product(
-            [RMSpropGraftingConfig] + get_all_subclasses(RMSpropGraftingConfig),
+            get_all_subclasses(RMSpropGraftingConfig),
             (-1.0, 0.0, 1.3),
         ):
             with self.subTest(cls=cls, beta2=beta2):
@@ -70,7 +86,8 @@ def test_illegal_beta2(
 class PreconditionerConfigSubclassesTest(unittest.TestCase):
     def test_illegal_num_tolerated_failed_amortized_computations(self) -> None:
         num_tolerated_failed_amortized_computations = -1
-        for cls in get_all_subclasses(PreconditionerConfig):
+        # Not testing for the base class PreconditionerConfig because it is an abstract class.
+        for cls in get_all_subclasses(PreconditionerConfig, include_cls_self=False):
             with self.subTest(cls=cls):
                 self.assertRaisesRegex(
                     ValueError,