java - Junit 外部资源@Rule 顺序

Question

我想在我的测试类中使用多个外部资源，但是外部资源的排序有问题。

这是代码片段：

public class TestPigExternalResource {

     // hadoop external resource, this should start first
     @Rule
     public HadoopSingleNodeCluster cluster = new HadoopSingleNodeCluster();

     // pig external resourcem, this should wait until hadoop external resource starts
     @Rule
     public  PigExternalResource pigExternalResource = new PigExternalResource(); 

     ...  
}

问题是它试图在 hadoop 启动之前启动 pig，因此我无法连接本地 hadoop 单节点集群。

有没有办法订购junit的规则？

谢谢

Answer 1

您可以使用RuleChain。

@Rule
public TestRule chain= RuleChain.outerRule(new HadoopSingleNodeCluster())
                           .around(new PigExternalResource());

Answer 2

您为什么不将这两个包装ExternalResources在您自己的中，按照您在新资源和方法中所需的顺序调用ExternalResource和before方法。afterbeforeafter

例子：

public class MyResource extends ExternalResource{
     private final List<ExternalResource> beforeResources;
     private final List<ExternalResource> afterResources;

     public MyResource(List<ExternalResource> beforeResources,
          List<ExternalResource> beforeResources){
     }

      public void before(){
          for (ExternalResource er : beforeResources)
               er.before();
      }

      public void after(){
          for (ExternalResource er : afterResources)
               er.after();
      }
}


public class TestPigExternalResource {

 // hadoop external resource, this should start first
 public HadoopSingleNodeCluster cluster = new HadoopSingleNodeCluster();

 // pig external resourcem, this should wait until hadoop external resource starts
 public  PigExternalResource pigExternalResource = new PigExternalResource(); 

  @Rule
  public MyResource myResource = new MyResource(
          newArrayList(cluster, pigExternalResource),
          newArrayList(cluster, pigExternalResource));
 ...  
}

Answer 3

从 JUnit 4.13-beta-1开始，有一个新的order属性。@Rule@ClassRule

见@Rule代码：

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.METHOD})
public @interface Rule {

    int DEFAULT_ORDER = -1;

    /**
     * Specifies the order in which rules are applied. The rules with a higher value are inner.
     *
     * @since 4.13
     */
    int order() default DEFAULT_ORDER;

}

另请参阅此 PR 以供参考：PR-1445。