Add unit tests for new is_model_blended function.

improver_tests/utilities/test_cube_checker.py

@@ -46,6 +46,7 @@
     check_cube_coordinates,
     check_for_x_and_y_axes,
     find_dimension_coordinate_mismatch,
+    is_model_blended,
     spatial_coords_match,
 )
 
@@ -301,5 +302,29 @@ def test_unmatching_y(self):
         self.assertFalse(result)
 
 
+class Test_is_model_blended(unittest.TestCase):
+
+    """Test is_model_blended behaves as expected."""
+
+    def setUp(self):
+        """Set up a cube."""
+        data = np.ones((1, 5, 5), dtype=np.float32)
+        cube = set_up_variable_cube(
+            data, "precipitation_amount", "kg m^-2", "equalarea",
+        )
+        self.cube_without = cube
+        blend_time = cube.coord("forecast_reference_time").copy()
+        blend_time.rename("blend_time")
+        self.cube_with = cube.copy()
+        self.cube_with.add_aux_coord(blend_time)
+
+    def test_basic(self):
+        """Test correct result is returned for cube with and without a
+        blend_time coordinate."""
+
+        self.assertFalse(is_model_blended(self.cube_without))
+        self.assertTrue(is_model_blended(self.cube_with))
+
+
 if __name__ == "__main__":
     unittest.main()