@Test public void shouldMergeTwoPriorityQueues() { final PriorityQueue<Integer> source = of(3, 1, 4, 1, 5); final PriorityQueue<Integer> target = of(9, 2, 6, 5, 3); assertThat(source.merge(target)).isEqualTo(of(3, 1, 4, 1, 5, 9, 2, 6, 5, 3)); assertThat(PriorityQueue.of(3).merge(PriorityQueue.of(toStringComparator(), 1))) .isEqualTo(of(3, 1)); }