@Test
public void notFinishedFutureReturnedIfPermitsAreNotGranted() {

    BufferedRateLimiter limiter = new BufferedRateLimiter(10, 1, 100);
    ListenableFuture<Void> actual1 = limiter.acquireAsync();
    ListenableFuture<Void> actual2 = limiter.acquireAsync();
    assertTrue(actual1.isDone());
    assertFalse(actual2.isDone());
}