Merge pull request #1020 from dstl/cgtm

Add type checking for model_list in CombinedGaussianTransitionModel

Resolves #1013

stonesoup/models/transition/base.py

@@ -34,6 +34,11 @@ class CombinedGaussianTransitionModel(TransitionModel, GaussianModel):
     """
     model_list: Sequence[GaussianModel] = Property(doc="List of Transition Models.")
 
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        if not isinstance(self.model_list, Sequence):
+            raise TypeError("model_list must be Sequence.")
+
     def function(self, state, noise=False, **kwargs) -> StateVector:
         """Applies each transition model in :py:attr:`~model_list` in turn to the state's
         corresponding state vector components.

stonesoup/models/transition/tests/test_combined.py

@@ -93,9 +93,22 @@ def test_nonlinear_combined(model_4):
         time_interval=t_delta).shape
     assert (DIM, 1) == combined_model.rvs(time_interval=t_delta).shape
 
-    # TODO: Figure out handling of pdf for non-linear models and singular convariance matrix
+    # TODO: Figure out handling of pdf for non-linear models and singular covariance matrix
     # e.g. See Non-Linear Constant Turn model
     # if isinstance(model_4,LinearModel):
     assert isinstance(
         combined_model.pdf(State(x_post), State(x_prior),
                            time_interval=t_delta), Real)
+
+
+@pytest.mark.parametrize(
+    "model_list",
+    [
+        ConstantVelocity(noise_diff_coeff=1),
+        CombinedGaussianTransitionModel([ConstantVelocity(1)]),
+        None,
+     ],
+    ids=["CV", "CGTM", "None"])
+def test_model_list(model_list):
+    with pytest.raises(TypeError):
+        CombinedGaussianTransitionModel(model_list)