Maven Surefire parallel='both'的工作方式与'methods'相同

Question

public class FirstTest {

  @Test
  public void test() throws InterruptedException {
    System.out.println(this.getClass() + " " + new Date());
    Thread.sleep(10_000);
  }

  @Test
  public void test2() throws InterruptedException {
    System.out.println(this.getClass() + " " + new Date());
    Thread.sleep(10_000);
  }

  @Test
  public void test3() throws InterruptedException {
    System.out.println(this.getClass() + " " + new Date());
    Thread.sleep(10_000);
  }

  @Test
  public void test4() throws InterruptedException {
    System.out.println(this.getClass() + " " + new Date());
    Thread.sleep(15_000);
  }

}

SecondTest类是相同的(10s+10s+10s+15s=45s)，而ThirdTest包含10s+10s+10s测试方法。

我使用的Maven Surefire插件配置如下：

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <version>2.9</version>
    <configuration>
      <excludes>
        <exclude>${excludeTestPath}</exclude>
      </excludes>
      <parallel>both</parallel>
      <threadCount>20</threadCount>
    </configuration>
</plugin>

我在理解并行属性是如何工作的方面有问题。我尝试设置“both”、“methods”和“classes”值，但得到了一些令人困惑的输出。请看一看，给我解释一下：

Concurrency config is parallel='classes', perCoreThreadCount=true, 
threadCount=20, useUnlimitedThreads=false
Running experiment.ThirdTest
class experiment.ThirdTest Mon Jun 10 12:00:38 CEST 2013
class experiment.ThirdTest Mon Jun 10 12:00:48 CEST 2013
class experiment.ThirdTest Mon Jun 10 12:00:58 CEST 2013
Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 30.024 sec
Running experiment.SecondTest
class experiment.SecondTest Mon Jun 10 12:00:38 CEST 2013
class experiment.SecondTest Mon Jun 10 12:00:48 CEST 2013
class experiment.SecondTest Mon Jun 10 12:00:58 CEST 2013
class experiment.SecondTest Mon Jun 10 12:01:08 CEST 2013
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 45.054 sec
Running experiment.FirstTest
class experiment.FirstTest Mon Jun 10 12:00:38 CEST 2013
class experiment.FirstTest Mon Jun 10 12:00:48 CEST 2013
class experiment.FirstTest Mon Jun 10 12:00:58 CEST 2013
class experiment.FirstTest Mon Jun 10 12:01:08 CEST 2013
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 45.074 sec

Results :
Tests run: 11, Failures: 0, Errors: 0, Skipped: 0

[INFO] Total time: 52.319s
[INFO] Finished at: Mon Jun 10 12:01:48 CEST 2013
[INFO] Final Memory: 22M/354M

Concurrency config is parallel='methods', perCoreThreadCount=true,
threadCount=20, useUnlimitedThreads=false
Running experiment.FirstTest
class experiment.FirstTest Mon Jun 10 12:10:23 CEST 2013
class experiment.FirstTest Mon Jun 10 12:10:23 CEST 2013
class experiment.FirstTest Mon Jun 10 12:10:23 CEST 2013
class experiment.FirstTest Mon Jun 10 12:10:23 CEST 2013
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 45.142 sec
Running experiment.SecondTest
class experiment.SecondTest Mon Jun 10 12:10:38 CEST 2013
class experiment.SecondTest Mon Jun 10 12:10:38 CEST 2013
class experiment.SecondTest Mon Jun 10 12:10:38 CEST 2013
class experiment.SecondTest Mon Jun 10 12:10:38 CEST 2013
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 45.037 sec
Running experiment.ThirdTest
class experiment.ThirdTest Mon Jun 10 12:10:53 CEST 2013
class experiment.ThirdTest Mon Jun 10 12:10:53 CEST 2013
class experiment.ThirdTest Mon Jun 10 12:10:53 CEST 2013
Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 30.009 sec

Results :
Tests run: 11, Failures: 0, Errors: 0, Skipped: 0

[INFO] Total time: 47.405s
[INFO] Finished at: Mon Jun 10 12:11:04 CEST 2013
[INFO] Final Memory: 22M/354M

Concurrency config is parallel='both', perCoreThreadCount=true, 
threadCount=20, useUnlimitedThreads=false
Running experiment.FirstTest
class experiment.FirstTest Mon Jun 10 12:18:40 CEST 2013
class experiment.FirstTest Mon Jun 10 12:18:40 CEST 2013
class experiment.FirstTest Mon Jun 10 12:18:40 CEST 2013
class experiment.FirstTest Mon Jun 10 12:18:40 CEST 2013
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 45.18 sec
Running experiment.SecondTest
class experiment.SecondTest Mon Jun 10 12:18:55 CEST 2013
class experiment.SecondTest Mon Jun 10 12:18:55 CEST 2013
class experiment.SecondTest Mon Jun 10 12:18:55 CEST 2013
class experiment.SecondTest Mon Jun 10 12:18:55 CEST 2013
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 45.031 sec
Running experiment.ThirdTest
class experiment.ThirdTest Mon Jun 10 12:19:10 CEST 2013
class experiment.ThirdTest Mon Jun 10 12:19:10 CEST 2013
class experiment.ThirdTest Mon Jun 10 12:19:10 CEST 2013
Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 30.025 sec

Results :
Tests run: 11, Failures: 0, Errors: 0, Skipped: 0

[INFO] Total time: 47.521s
[INFO] Finished at: Mon Jun 10 12:19:20 CEST 2013
[INFO] Final Memory: 22M/354M

Answer 1

参见SUREFIRE-814（2012年1月）的这条评论：

“两者”在很长一段时间内基本上没有经过测试，我没有理由不相信你看到了这个问题。

可以肯定的是，在此期间，两者都没有受到太多的关注。我证实了这个问题影响到Surefire 2.15，我计划就此发表评论并对该票进行投票（一旦我得到我的注册确认）。我建议更多的人投票。