diff --git a/pyproject.toml b/pyproject.toml
index d302995..71d429d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -136,6 +136,7 @@ lines-after-imports = 2
 
 [tool.mypy]
 mypy_path = ["src"]
+files = ["src", "testing"]
 # TODO: Enable this & fix errors.
 # check_untyped_defs = true
 disallow_any_generics = true