Fix test typing

Previously there was a test which violated type-hints.
As we can not keep having the test _and_ type hints on that test, the
test itself was rewritten to test a semantically slightly different but
similar edge case.
The original test case is of course prevented when using type-hints (i.e
not passing `None` to a function that doesn't accept `None`)

Signed-off-by: Florian Wagner <[email protected]>

Author: florian-wagner-frequenz

tests/config/test_util.py

@@ -54,13 +54,14 @@ def test_load_config_dataclass(
     [SimpleConfig, MmSimpleConfig],
     ids=["dataclass", "marshmallow_dataclass"],
 )
-def test_load_config_load_None(
+@pytest.mark.parametrize("config", [dict(), None], ids=["empty", "none"])
+def test_load_config_load_empty(
     config_class: type[SimpleConfig] | type[MmSimpleConfig],
+    config: dict[str, Any] | None,
 ) -> None:
-    """Test that load_config raises ValidationError if the configuration is None."""
-    config: dict[str, Any] = {}
+    """Test that load_config raises ValidationError if the configuration is empty."""
     with pytest.raises(marshmallow.ValidationError):
-        _ = load_config(config_class, config.get("loggers", None))
+        _ = load_config(config_class, config)  # type: ignore[arg-type]
 
 
 @pytest.mark.parametrize(