def METHOD_NAME(self):
    """Test that an exception is raised for negative values of
    probability_of_sleet in the cube."""
    rain = self.rain_prob_cube
    high_prob = self.high_prob_cube
    msg = "Negative values of sleet probability have been calculated."
    with self.assertRaisesRegex(ValueError, msg):
        calculate_sleet_probability(rain, high_prob)