Skip tests with missing optional dependencies

Author: dnerini

pysteps/tests/test_motion.py

@@ -194,6 +194,8 @@ def test_optflow_method_convergence(input_precip, optflow_method_name,
             - linear_x: (u=2, v=0)
             - linear_y: (u=0, v=2)
     """
+    if optflow_method_name == 'lk':
+        pytest.importorskip('cv2')
 
     ideal_motion, precip_obs = _create_observations(input_precip.copy(),
                                                     motion_type,
@@ -264,6 +266,8 @@ def test_no_precipitation(optflow_method_name, num_times):
         Number of precipitation frames (times) used as input for the optical
         flow methods.
     """
+    if optflow_method_name == 'lk':
+        pytest.importorskip('cv2')
     zero_precip = np.zeros((num_times,) + reference_field.shape)
     motion_method = motion.get_method(optflow_method_name)
     uv_motion = motion_method(zero_precip, verbose=False)
@@ -286,6 +290,8 @@ def test_no_precipitation(optflow_method_name, num_times):
 def test_input_shape_checks(optflow_method_name,
                             minimum_input_frames,
                             maximum_input_frames):
+    if optflow_method_name == 'lk':
+        pytest.importorskip('cv2')
     image_size = 100
     motion_method = motion.get_method(optflow_method_name)
 

pysteps/tests/test_nowcasts_steps.py

@@ -46,6 +46,7 @@ def test_steps(
                                           upscale=2000)[1:, :, :]
 
     # Retrieve motion field
+    pytest.importorskip('cv2')
     oflow_method = motion.get_method("LK")
     retrieved_motion = oflow_method(precip_input)