带有代码调用任务的单元测试同步方法

Question

Given the following class:

public class TestAttribute : ActionFilterAttribute
{
    public bool SomeExampleBool = false;

    public override void OnActionExecuting(HttpActionContext actionContext)
    {
        Task.Factory.StartNew(() => { SomeExampleBool = true; });
    }
}

How would you write a valid unit test for OnActionExecuting that Asserts that SomeExampleBool is equal to true ?

When writing a unit test and calling OnActionExecuting , then calling the Assert, the logic executes on a thread that will not have executed yet. So the Assert fails. Would you try something like Thread.Sleep for a couple of seconds? Seems like a hack. I'm sure there is a better way that I'm not thinking of but I'm reaching out to the community for some help.

Answer 1

You'll need to expose the Task returned by StartNew to anyone that you want to be able to:

1. Know when the operation finishes (by adding a continuation to it)
2. Know what the result is, if applicable
3. Know what any exceptions were, if applicable
4. Know if it was cancelled
5. Wait until it has finished

Since you're not exposing the return Task to anyone, you're just dropping it on the floor, there's no way for anyone else to wait on it, or run a continuation when it's done. Typically you'd return the Task from that method. If you can't, because it's an event handler, then you could potentially store the Task in a field or some other form of state that the caller would be able to access.

Answer 2

Task.Factory.StartNew will return an instance of a Task . If you call task.Wait() , you'll be guaranteed that the task will complete before executing the next line. You should be able to just Wait for the task to complete, and then run your assertions after that.