@Test
public void testCompareIsTransitiveWhenServiceReferencePropertiesAreNull() {

	PropertyServiceReferenceComparator<Object>
		propertyServiceReferenceComparator =
			new PropertyServiceReferenceComparator<>("ranking");
	ServiceReference<Object> serviceReference1 = new TestServiceReference<>(
		"ranking", -1);
	ServiceReference<Object> serviceReference2 = new TestServiceReference<>(
		"ranking", 0);
	ServiceReference<Object> serviceReference3 = new TestServiceReference<>(
		"ranking", 1);
	ServiceReference<Object> serviceReference4 =
		new TestServiceReference<>();
	int compare1 = propertyServiceReferenceComparator.compare(
		serviceReference4, serviceReference1);
	Assert.assertTrue(compare1 > 0);
	int compare2 = propertyServiceReferenceComparator.compare(
		serviceReference1, serviceReference2);
	Assert.assertTrue(compare2 > 0);
	int compare3 = propertyServiceReferenceComparator.compare(
		serviceReference4, serviceReference2);
	Assert.assertTrue(compare3 > 0);
	int compare4 = propertyServiceReferenceComparator.compare(
		serviceReference4, serviceReference2);
	Assert.assertTrue(compare4 > 0);
	int compare5 = propertyServiceReferenceComparator.compare(
		serviceReference2, serviceReference3);
	Assert.assertTrue(compare5 > 0);
	int compare6 = propertyServiceReferenceComparator.compare(
		serviceReference4, serviceReference3);
	Assert.assertTrue(compare6 > 0);
}