@Test
public void testDifferenceEmptyPositiveCase() {

	Collection<String> a = new ArrayList<>();
	a.add("i1");
	a.add("i2");
	a.add("i3");
	Collection<String> b = new HashSet<>();
	b.add("i1");
	b.add("i2");
	b.add("i3");
	assertTrue("Difference IS empty, but SetUtil.differenceEmpty returns false", SetUtil.differenceEmpty(a, b));
}