@Test public void testClear() { list.addTail(a, 0); list.addTail(b, 3); list.addTail(c, 3); list.addTail(d, 3); list.addTail(e, 6); list.addTail(f, 6); list.addTail(g, 6); list.addTail(h, 9); list.addTail(i, 9); list.addTail(j, 9); list.clear(); Assert.assertNull(list.poll()); }