@Test
public void lifecycleStartStartsPoolOnlyOnce() {

    // given
    PoolingAsyncResponseConsumerFactory asyncResponseConsumerFactory =
            mock(PoolingAsyncResponseConsumerFactory.class);
    HttpClient httpClient = createTestHttpClient(
            mock(CloseableHttpAsyncClient.class),
            mock(ServerPool.class),
            mock(RequestFactory.class),
            asyncResponseConsumerFactory);
    // when
    httpClient.start();
    httpClient.start();
    // then
    verify(asyncResponseConsumerFactory, times(1)).start();
}