assertFreshInstanceReturned(Random.class);
    assertEquals(
        ArbitraryInstances.get(Random.class).nextInt(),
        ArbitraryInstances.get(Random.class).nextInt());
  }

  public void testGet_concurrent() {
    assertTrue(ArbitraryInstances.get(BlockingDeque.class).isEmpty());
    assertTrue(ArbitraryInstances.get(BlockingQueue.class).isEmpty());
    assertTrue(ArbitraryInstances.get(DelayQueue.class).isEmpty());