def METHOD_NAME(self):
    """Tests that a ValueError is raised if the input contains
    values that are not a number. """
    self.cube_uv_down.data.fill(np.nan)
    msg = (
        "The radiation flux in UV downward contains data "
        "that is negative or NaN. Data should be >= 0."
    )
    with self.assertRaisesRegex(ValueError, msg):
        calculate_uv_index(self.cube_uv_down)