Asp.net MVC: Testing a custom Authorize filters

Asp.net MVC let you intercept the actions via a feature they call: Filters. Filters are just attributes that you decorate into actions and them allow to you make an stop before or after the action-methods are executed (also are filters to intercept code before/after the result is executed, errors are thrown, etc). There are a few kind of Filter attributes, in the picture bellow into the blue square you’ve what filters came supported out-of-the-box.

Today we are going to talk about the AuthorizeAttribute and how to extend and test it.

AuthorizeAttribute (from the Msdn):

Represents an attribute that is used to restrict access by callers to an action method.

This filter is the first to be called when the Controller Action Invoker try to run Action methods. You can set into the attribute which are the Users or Roles can execute an Action, if the User/Role doesn?t fulfill with what was established into the Action an Unauthorized Result is raised. Remember that exactly after the filter execution ended in a ActionResult, that result is executed.

Now, let?s go to the hypothetical scenario that you need a custom authorization schema, that you need more than User/Role, or you just need neither of both, because your model is based on a Security Level. So you don?t care about who is the guy? / or what role it has?, you just need the security level it has.

With this scenario you can write a custom Authorize attribute:

In this CustomAuthorize attribute, we are doing first the well known authorization (which is, executing the code as is in the class base). When that authorization part passed, we go through our custom authorization part: we get the user from the Database (or whatever other source) and we check the security level. If it?s allowed to execute the action-method we end without setting the result. If it?s not, we set a HttpUnauthorizedResult. In the browser you will be redirected to the login page if you?re not allowed to execute that code.

Now the problem is when you need to test the authorization. Actually you can do it with some mock and overriding some code.

Another thing you?ve to know is that the object in charge of execute the actions is the ControllerActionInvoker. Then to invoke and action into your tests and see the result when the filters are invoked, we need to customize some, and override the method in charge of execute the result (the ActionResult), which is InvokeActionResult. Where is how should looks our method override:

Assert is a class from a Unit Testing framework, in this case in the example is using the Unit Testing framework that came with Visual Studio because every user can run the tests without have ie: Resharper installed. This Assert is expecting that the Result from the filter/action execution is the same with the TResult (is a generic parameter declared into the class). So with this class, we can make an easy test to see if the result is authorized or unauthorized.

Our test for authorized access, should be looking like this

First we are creating a new Controller, we mock stuff for authentication, and then using our custom action invoker to try to invoke the action using InvokeAction method (passing the Context and the Action name to be executed).

We are using some extensions and helpers methods, i.e.: SetFakeAuthenticatedContext is included into the example and there you?ll see which elements you need to mock when use Authorize filter-attributes.

To understand what happened in this first test method:

  1. Controller creation
  2. Mock authentication stuff using our user named:?pepe?.
  3. Using the custom invoker we launch the action ?PermisiveAction?.
  4. The CustomAuthorized filter is raised, it pass the authorization.
  5. The action is executed and return a ViewResult (doing return View() into the code).
  6. The Assertion is made, everything ok and the test pass.

And now let?s see this another test

The difference with the previous one is in the step 4, 5 and 6. The action is not executed because the filter raise an HttpUnauthorizedResult. Download the example to understand better how to manage the testing of Authorization on Actions.

Download code example

  • http://www.fullmobile.com Car Market

    This is wonderful. Other than what the filter does, I think demonstrating how to test an action with its filter is the true value here….
    Just perfect

  • http://www.limeboy.com Mike Pollitt

    This is brilliant. I agree with Car Market – the great value here is setting up the ability to test controller actions where filters have been applied.

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  • John Adaikalasamy

    nice one, Thank you very much.

  • John Zabroski

    Your test is basically not enough for an integration test, and also too complicated for a unit test. Also, none of your authorization logic will be re-usable outside of MVC. Extract the logic for your custom attribute into a helper method, and test that helper method instead. Separately, test that your ChangePassword controller action contains the attribute you expect, so that if it is ever removed, your tests fail.