ms = new MultiSet<>(l1).append(l2); assertObjectEquals("['1','2','3','4']", ms); assertObjectEquals("['1','2','3','4']", ms.enumerator()); assertEquals(4, ms.size()); t.next(); t.remove(); assertObjectEquals("['2','3','4']", ms.enumerator()); assertObjectEquals("['3','4']", ms.enumerator()); assertObjectEquals("['4']", ms.enumerator()); assertObjectEquals("[]", ms.enumerator()); assertEquals(0, ms.size());