Junit5 源码分析系列（四）

测开技术笔记 2021-04-18

562

前面讲了测试用例相关的数据结构是怎么生成的，当框架解析了测试用例后，后面就是执行了。执行方法的入口在DefaultLauncher.execute()方法

@Override
  public void execute(LauncherDiscoveryRequest discoveryRequest, TestExecutionListener... listeners) {
    ......
    execute(InternalTestPlan.from(discoverRoot(discoveryRequest, "execution")), listeners);
  }


  @Override
  public void execute(TestPlan testPlan, TestExecutionListener... listeners) {
    ......
    execute((InternalTestPlan) testPlan, listeners);
  }
  
  private void execute(InternalTestPlan internalTestPlan, TestExecutionListener[] listeners) {
    Root root = internalTestPlan.getRoot();
    ConfigurationParameters configurationParameters = root.getConfigurationParameters();
    TestExecutionListenerRegistry listenerRegistry = buildListenerRegistryForExecution(listeners);
    //构造lambda表达式，遍历testEngine，分别执行其中的testDescriptor 
    withInterceptedStreams(configurationParameters, listenerRegistry, testExecutionListener -> {
      ......
      ExecutionListenerAdapter engineExecutionListener = new ExecutionListenerAdapter(internalTestPlan,
        testExecutionListener);
      //循环遍历testEngine 中的estDescriptor ，依次执行
      for (TestEngine testEngine : root.getTestEngines()) {
        TestDescriptor testDescriptor = root.getTestDescriptorFor(testEngine);
        execute(testEngine,
          //构造ExecutionRequest对象
          new ExecutionRequest(testDescriptor, engineExecutionListener, configurationParameters));
      }
      ......
    });
  }

实际依次调用执行了三个execute方法，最后execute执行的参数是构造的InternalTestPlan对象，使用InternalTestPlan.from()方法生成

static InternalTestPlan from(Root root) {
    //生成委托对象，传入前面解析完成的根节点TestDescriptor即JupiterEngineDescriptor
    TestPlan delegate = TestPlan.from(root.getEngineDescriptors());
    return new InternalTestPlan(root, delegate);
  }
  
  
  public static TestPlan from(Collection<TestDescriptor> engineDescriptors) {
    Preconditions.notNull(engineDescriptors, "Cannot create TestPlan from a null collection of TestDescriptors");
    TestPlan testPlan = new TestPlan(engineDescriptors.stream().anyMatch(TestDescriptor::containsTests));
    //添加到testPlan中的allIdentifiers map中
    Visitor visitor = descriptor -> testPlan.add(TestIdentifier.from(descriptor));
    engineDescriptors.forEach(engineDescriptor -> engineDescriptor.accept(visitor));
    return testPlan;
  }

在withInterceptedStreams方法中，主要就是执行lambda表达式，所以重点还是execute(InternalTestPlan internalTestPlan, TestExecutionListener[] listeners)方法中的lambda表达式，如上述中循环遍历testEngine根节点，调用第四个execute方法 execute(TestEngine testEngine, ExecutionRequest executionRequest)执行，在其中调用testEngine的execute方法执行，入参ExecutionRequest 是一个包装类，主要包含TestDescriptor对象和EngineExecutionListener监听器对象

private void withInterceptedStreams(ConfigurationParameters configurationParameters,
      TestExecutionListenerRegistry listenerRegistry, Consumer<TestExecutionListener> action) {
    //获取CompositeTestExecutionListener，实际是个组合类，listener的组合，
    //其中主要调用notifyEach 方法依次执行所有的listener对应的方法，如executionStarted,executionFinished等
    TestExecutionListener testExecutionListener = listenerRegistry.getCompositeTestExecutionListener();
    ......
    try {
      //执行lambda表达式
      action.accept(testExecutionListener);
    }
    finally {
       ......
    }
  }
  
  
  private void execute(TestEngine testEngine, ExecutionRequest executionRequest) {
    try {
      //调用engine的excute方法
      testEngine.execute(executionRequest);
    }
    catch (Throwable throwable) {
      handleThrowable(testEngine, "execute", throwable);
    }
  }

说到testEngine的execute方法，我们先看看JupiterTestEngine的继承结构，如下图所示：

由于JupiterTestEngine中没有实现execute方法，会直接调用父类HierarchicalTestEngine中的execute方法

@Override
public final void execute(ExecutionRequest request) {
    //创建执行器service，如果没有并非执行相关配置，默认直接返回单线程执行器service
    //这里返回默认执行器service - SameThreadHierarchicalTestExecutorService
    try (HierarchicalTestExecutorService executorService = createExecutorService(request)) {
      //创建<C extends EngineExecutionContext>，这里返回JupiterEngineExecutionContext对象
      C executionContext = createExecutionContext(request);
      //返回包含 TestAbortedException（依赖于opentest4j库）  Predicate<? super Throwable> 的 OpenTest4JAwareThrowableCollector
      ThrowableCollector.Factory throwableCollectorFactory = createThrowableCollectorFactory(request);
      //调用HierarchicalTestExecutor的execute方法，并get取得结果
      new HierarchicalTestExecutor<>(request, executionContext, executorService,
        throwableCollectorFactory).execute().get();
    }
    catch (Exception exception) {
      throw new JUnitException("Error executing tests for engine " + getId(), exception);
    }
  }
  
  //HierarchicalTestExecutor 的execute方法
  Future<Void> execute() {
    TestDescriptor rootTestDescriptor = this.request.getRootTestDescriptor();
    EngineExecutionListener executionListener = this.request.getEngineExecutionListener();
    //walk方法解决资源竞争的问题，当前不涉及
    NodeExecutionAdvisor executionAdvisor = new NodeTreeWalker().walk(rootTestDescriptor);
    //通过listener,executionService，throwableCollectorFactory，executionAdvisor构造taskContext
    NodeTestTaskContext taskContext = new NodeTestTaskContext(executionListener, this.executorService,
      this.throwableCollectorFactory, executionAdvisor);
    //通过taskContext和 根testDescriptor构造NodeTestTask对象，这个对象是后面执行测试用例的关键
    NodeTestTask<C> rootTestTask = new NodeTestTask<>(taskContext, rootTestDescriptor);


    rootTestTask.setParentContext(this.rootContext);
    //提交给executorService执行NodeTestTask
    return this.executorService.submit(rootTestTask);
  }

NodeTestTask 是执行测试用例的关键，下节将详细讲解其执行流程。

To be continued...

数据库

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Junit5 源码分析系列（四）

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