如何测试ActionFilterAttribute - OnActionExecuted

Question

I am trying to unit test a custom ActionFilterAttribute. For example:

public class ActionAuthorizationAttribute: ActionFilterAttribute 
{

  protected override void  OnActionExecuted(ActionExecutedContext filterContext)
  {
    filterContext.HttpContext.Response.Redirect("SecurityException");
  }
}

How can I write a unit test that would test that any action that would have this attribute would redirect to SecurityException.

My Attempt

[TestClass]
public class TestControllerResponse
{
  [TestMethod]
  public void TestPermissionAccepted()
  {
    var controller = new TestController();
    var result = controller.Index() as RedirectToRouteResult;
    Assert.IsNotNull(result);
    Assert.AreEqual("SecurityException", result.RouteValues["action"]);
  }
}

protected class TestController : Controller
{
  [ActionAuthorization]
  public ActionResult Index()
  {
    return RedirectToAction("UnfortunatelyIWasCalled");
  }

}

Unfortunately, the test fails. The index action redirects to "UnfortunatelyIWasCalled" instead of "SecurityException".

Answer 1

I would not Unit Test the Controller's Action to test the behaviour of an Action Filter. They are two separate concerns. For example, if someone goes and changes the ActionAuthorizeAttribute's OnActionExecutedMethod to return a different exception, your Unit Test on the Controller's Action going to fail for the wrong reason. This is because, you are testing the Action, but your code also testing something else in within an ActionFilter. Unit Testing is all about verifying the behaviour of a Unit of work in isolation. If you really want to test the ActionFilter, I would Unit Test the filter separately. Whether the ActionFilter get called after your Action gets executed is a separate concern and that has been already tested by the MVC framework.