add type annotations for adaptive/tests/test_skopt_learner.py

Author: basnijholt

adaptive/tests/test_skopt_learner.py

@@ -10,7 +10,7 @@
 
 
 @pytest.mark.skipif(not with_scikit_optimize, reason="scikit-optimize is not installed")
-def test_skopt_learner_runs():
+def test_skopt_learner_runs() -> None:
     """The SKOptLearner provides very few guarantees about its
        behaviour, so we only test the most basic usage
     """
@@ -26,7 +26,7 @@ def g(x, noise_level=0.1):
 
 
 @pytest.mark.skipif(not with_scikit_optimize, reason="scikit-optimize is not installed")
-def test_skopt_learner_4D_runs():
+def test_skopt_learner_4D_runs() -> None:
     """The SKOptLearner provides very few guarantees about its
        behaviour, so we only test the most basic usage
        In this case we test also for 4D domain