<h3>1.背景</h3>    <p>在编写自动化测试用例过程中，往往会遇见被测代码有异步或者队列处理的中间过程；如果需要校验这部分结果，必须等待异步操作结束或队列消费完，而这个中间等待的时间是不确定的，常常是根据经验值设定，通过 Thread.sleep(经验值) ，而这个时间通常会设置成最长的那次时间，但是可能99%次这个异步操作都低于这个最长的时间，这就造成了每次执行这个测试用例都花费了异步任务最长的那次时间。</p>    <p>现介绍一款开源工具awaitility: <a href="/misc/goto?guid=4959728949104437685" rel="nofollow,noindex">https://github.com/awaitility/awaitility</a> ，该工具提供轮询的方式，判断操作是否完成，以最短的时间获取异步任务结果。</p>    <h3>2.入门</h3>    <p>awaitility支持Java、Scala、Groovy，本文以Java介绍。</p>    <p>maven工程在pom.xml添加awaitility依赖：</p>    <pre>  <code class="language-java"><dependency>        <groupId>org.awaitility</groupId>        <artifactId>awaitility</artifactId>        <version>2.0.0</version>        <scope>test</scope>  </dependency></code></pre>    <h3>3.实例</h3>    <p>测试类import相关Class：</p>    <pre>  <code class="language-java">import java.util.concurrent.Callable;  import static java.util.concurrent.TimeUnit.*;    import static org.awaitility.Awaitility.*;  import static org.awaitility.Duration.*;  import static org.awaitility.pollinterval.FibonacciPollInterval.*;</code></pre>    <p>构造一个异步任务：</p>    <pre>  <code class="language-java">interface CounterService extends Runnable {          int getCount();      }      // 每隔1s, count累加1      class CounterServiceImpl implements CounterService {          private volatile int count = 0;          public void run() {              new Thread(new Runnable() {                  @Override                  public void run() {                      try {                          for(int index = 0; index < 5; index++) {                              Thread.sleep(1000);                              count += 1;                          }                      } catch (InterruptedException e) {                          throw new RuntimeException(e);                      }                  }              }).start();          }          public int getCount() {              return count;          }      }</code></pre>    <p>3-1.默认等待时间</p>    <p>await().until(Callable conditionEvaluator)最多等待10s直到conditionEvaluator满足条件，否则ConditionTimeoutException。</p>    <pre>  <code class="language-java">@Test      public void testAsynchronousNormal(){          final CounterService service = new CounterServiceImpl();          service.run();          try{              // 默认10s, 如果在这时间段内,条件依然不满足,将抛出ConditionTimeoutException              await().until(new Callable<Boolean>() {                  @Override                  public Boolean call() throws Exception {                      return service.getCount() == 5;                  }              });          } catch (Exception e) {              Assert.fail("测试代码运行异常：" + e.getMessage() + "，代码位置：" + e.getStackTrace()[0].toString());          }      }</code></pre>    <p>默认超时时间为10s, 可通过setDefaultTimeout()自定义默认超时时间。</p>    <p>3-2.最多等待</p>    <p>await().atMost() 设置最多等待时间，如果在这时间内条件还不满足，将抛出ConditionTimeoutException。</p>    <pre>  <code class="language-java">@Test      public void testAsynchronousAtMost(){          final CounterService service = new CounterServiceImpl();          service.run();          try{              // 指定超时时间3s, 如果在这时间段内,条件依然不满足,将抛出ConditionTimeoutException              await().atMost(3, SECONDS).until(new Callable<Boolean>() {                  @Override                  public Boolean call() throws Exception {                      return service.getCount() == 5;                  }              });          } catch (Exception e) {              Assert.fail("测试代码运行异常：" + e.getMessage() + "，代码位置：" + e.getStackTrace()[0].toString());          }      }</code></pre>    <p>3-3.至少等待</p>    <p>await().atLeast() 设置至少等待时间；多个条件时候用and()连接。</p>    <pre>  <code class="language-java">@Test      public void testAsynchronousAtLeast(){            final CounterService service = new CounterServiceImpl();          service.run();            try{              // 指定至少1s, 最多3s, 如果在这时间段内,条件依然不满足,将抛出ConditionTimeoutException              await().atLeast(1, SECONDS).and().atMost(3, SECONDS).until(new Callable<Boolean>() {                  @Override                  public Boolean call() throws Exception {                      return service.getCount() == 2;                  }              });            } catch (Exception e) {              Assert.fail("测试代码运行异常：" + e.getMessage() + "，代码位置：" + e.getStackTrace()[0].toString());            }      }</code></pre>    <p>3-4.forever等待</p>    <p>forever等待，不推荐使用，可能导致死循环。</p>    <pre>  <code class="language-java">await().forever().until(new Callable<Boolean>() {                  @Override                  public Boolean call() throws Exception {                      return service.getCount() == 6;                  }              });</code></pre>    <p>3-5.轮询</p>    <p>with().pollInterval(ONE_HUNDRED_MILLISECONDS).and().with().pollDelay(50, MILLISECONDS) that is conditions are checked after 50ms then 50ms+100ms。</p>    <pre>  <code class="language-java">@Test      public void testAsynchronousPoll(){          final CounterService service = new CounterServiceImpl();          service.run();          try{              // 轮询查询,pollInterval每隔多少时间段轮询, pollDelay每次轮询间隔时间              with().pollInterval(ONE_HUNDRED_MILLISECONDS).and().with().pollDelay(50, MILLISECONDS).await("count is greater 3").until(                      new Callable<Boolean>() {                          @Override                          public Boolean call() throws Exception {                              return service.getCount() == 4;                          }                      });          } catch (Exception e) {              Assert.fail("测试代码运行异常：" + e.getMessage() + "，代码位置：" + e.getStackTrace()[0].toString());          }      }</code></pre>    <p>3-6.Fibonacci轮询</p>    <p>with().pollInterval(fibonacci(SECONDS))非线性轮询，按照fibonacci数轮询。</p>    <pre>  <code class="language-java">@Test      public void testAsynchronousFibonacciPoll(){          final CounterService service = new CounterServiceImpl();          service.run();          try{              // 使用fibonacci数作为间隔数1,1,2,3,5,8,..., 默认单位milliseconds         with().pollInterval(fibonacci(SECONDS)).await("count is greater 3").until(                      new Callable<Boolean>() {                          @Override                          public Boolean call() throws Exception {                              return service.getCount() == 4;                          }                      });          } catch (Exception e) {              Assert.fail("测试代码运行异常：" + e.getMessage() + "，代码位置：" + e.getStackTrace()[0].toString());          }      }</code></pre>    <p> </p>    <p>来自：http://blog.csdn.net/neven7/article/details/55004939</p>    <p> </p>