相关疑难解决方法(0)

我正在为我的应用程序的"粘合"层编写单元测试,并且很难为异步方法创建确定性测试,允许用户过早地取消操作.

具体来说,在一些异步方法中,我们有代码响应取消调用并确保对象在完成之前处于正确状态.我想确保测试涵盖这些代码路径.

在此场景中举例说明典型异步方法的一些C#伪代码如下:

public void FooAsync(CancellationToken token, Action<FooCompletedEventArgs> callback) 
{
   if (token.IsCancellationRequested) DoSomeCleanup0();

   // Call the four helper methods, checking for cancellations in between each
   Exception encounteredException;
   try
   {
      MyDependency.DoExpensiveStuff1();
      if (token.IsCancellationRequested) DoSomeCleanup1();

      MyDependency.DoExpensiveStuff2();
      if (token.IsCancellationRequested) DoSomeCleanup2();

      MyDependency.DoExpensiveStuff3();
      if (token.IsCancellationRequested) DoSomeCleanup3();

      MyDependency.DoExpensiveStuff4();
      if (token.IsCancellationRequested) DoSomeCleanup4();

   }
   catch (Exception e)
   {
      encounteredException = e;
   }

   if (!token.IsCancellationRequested)
   {
      var args = new FooCompletedEventArgs(a bunch of params);
      callback(args);
   }
}

到目前为止,我提出的解决方案涉及模拟MyDependency由胶层包裹的基础操作,并强制每个人在任意时间段内休眠.然后我调用异步方法,并告诉我的单元测试在取消异步请求之前休眠几毫秒.

像这样的东西(以Rhino Mocks为例):

[TestMethod]
public void FooAsyncTest_CancelAfter2()
{
   // arrange …