How do I unit test a controller action that uses ther Controller.User variable?

Question

I have a controller action that automatically redirects to a new page if the user is already logged in (User.Identity.IsAuthenticated). What is the best way to writ

Answer 1

That's not the simplest thing to do, but it can be done. The User property simply delegates to Controller.HttpContext.User. Both are non-virtual read-only properties, so you can't do anything about them. However, Controller.HttpContext delegates to ControllerBase.ControllerContext which is a writable property.

Therefore, you can assign a Test Double HttpContextBase to Controller.ControllerContext before exercising your System Under Test (SUT). Using Moq, it would look something like this:

var user = new GenericPrincipal(new GenericIdentity(string.Empty), null);
var httpCtxStub = new Mock();
httpCtxStub.SetupGet(ctx => ctx.User).Returns(user);

var controllerCtx = new ControllerContext();
controllerCtx.HttpContext = httpCtxStub.Object;

sut.ControllerContext = controllerCtx;

Then invoke your action and verify that the return result is a RedirectResult.

This test utilizes the implicit knowledge that when you create a GenericIdentity with an empty name, it will return false for IsAuthenticated. You could consider making the test more explicit by using a Mock instead.