@Test(expected = IllegalArgumentException.class)
public void testDownsampleTransformWithoutMetrics() {

    Transform downsampleTransform = new DownsampleTransform();
    List<Metric> metrics = null;
    List<String> constants = new ArrayList<String>();
    constants.add("2");
    constants.add("average");
    downsampleTransform.transform(null, metrics, constants);
}