def METHOD_NAME(self):
    """Test it raises a Value Error if not supplied with a cube. """
    plugin = LinearWeights(y0val=20.0, ynval=2.0)
    notacube = 0.0
    msg = "The first argument must be an instance of " "iris.cube.Cube"
    with self.assertRaisesRegex(TypeError, msg):
        plugin.process(notacube, self.coord_name)