tests: add type annotations to Smart tests (#1686)

Add type annotations across all 'smart' tests, enabling mypy to check test function bodies, catching type errors that were previously hidden.

tests/smart/modules/test_mop.py

@@ -20,7 +20,9 @@ mop = parametrize("has mop", component_filter="mop", protocol_filter={"SMART"})
         ("mop_waterlevel", "waterlevel", str),
     ],
 )
-async def test_features(dev: SmartDevice, feature: str, prop_name: str, type: type):
+async def test_features(
+    dev: SmartDevice, feature: str, prop_name: str, type: type
+) -> None:
     """Test that features are registered and work as expected."""
     mod = next(get_parent_and_child_modules(dev, Module.Mop))
     assert mod is not None
@@ -34,7 +36,7 @@ async def test_features(dev: SmartDevice, feature: str, prop_name: str, type: ty
 
 
 @mop
-async def test_mop_waterlevel(dev: SmartDevice, mocker: MockerFixture):
+async def test_mop_waterlevel(dev: SmartDevice, mocker: MockerFixture) -> None:
     """Test dust mode."""
     mop_module = next(get_parent_and_child_modules(dev, Module.Mop))
     call = mocker.spy(mop_module, "call")