diff --git a/lib/python/base_cli/testing.py b/lib/python/base_cli/testing.py
index c60f6d4..36dc7ec 100644
--- a/lib/python/base_cli/testing.py
+++ b/lib/python/base_cli/testing.py
@@ -13,6 +13,9 @@
     from click.testing import Result
 
 
+__all__ = ["invoke"]
+
+
 _INVOKE_CWD_LOCK = RLock()
 
 
diff --git a/tests/test_public_api.py b/tests/test_public_api.py
index ce56f99..626e96c 100644
--- a/tests/test_public_api.py
+++ b/tests/test_public_api.py
@@ -160,6 +160,7 @@ def test_module_all_surfaces_are_explicit(self) -> None:
             },
         )
         self.assertEqual(set(deprecations.__all__), {"BaseCliDeprecationWarning", "deprecated"})
+        self.assertEqual(base_cli.testing.__all__, ["invoke"])
 
     def test_entry_points_have_docstrings(self) -> None:
         self.assertTrue(base_cli.App.__doc__)