@Test
  public void acquireAfterCloseFails() throws InterruptedException {
    ChannelPool connectionPool = mock(ChannelPool.class);
    Http2MultiplexedChannelPool h2Pool =
        new Http2MultiplexedChannelPool(connectionPool, loopGroup.next(), new HashSet<>(), null,
            http2ClientConfigForOneConnection, new Http2ClientMetrics(new MetricRegistry()), streamChannelInitializer);

    h2Pool.close();

    Future<Channel> acquireResult = h2Pool.acquire().await();
    assertFalse(acquireResult.isSuccess());
    assertTrue(acquireResult.cause() instanceof IOException);
  }
Acquire should fail if pool is closed.
ambry-network/src/test/java/com/github/ambry/network/http2/Http2MultiplexedChannelPoolTest.java