NullReferenceException when using Rhino Mocks

While writing some tests for the following method I had a strange problem. When the test ran it threw a NullReferenceExceptions for my stubbed User object.

The method under test is simple enough

	public void SetCookie(IHttpContextService context)
	{
	if (context == null)
	return;
	if (context.User == null)
	return;
	if (context.User.Identity == null)
	return;
	if (!context.User.Identity.IsAuthenticated)
	return;
	this.UserName = context.User.Identity.Name;
	// Create a cookie for username and key
	var cookie = new HttpCookie("Token", this.UserNameOnly + "|" + GetKey(this.Input));
	context.CookieCollection.Add(cookie);
	}

view raw example1.cs hosted with ❤ by GitHub

as is the test case

	[Test]
	public void Should_SetACookie()
	{
	var httpContextService = MockRepository.GenerateStub<IHttpContextService>();
	var cookieCollection = new HttpCookieCollection();
	IPrincipal user = new GenericPrincipal(new GenericIdentity("Test"),
	new[] {"TestRole"});
	httpContextService.Stub(c => c.User).Return(user);
	httpContextService.Stub(c => c.CookieCollection).Return(cookieCollection);
	cookieSetter.SetCookie(httpContextService);
	httpContextService.VerifyAllExpectations();
	}

view raw example2.cs hosted with ❤ by GitHub

The mocking Framework is Rhino Mocks and this was the solution to the problem.

With Rhino a call to a stub (or mock) is expected only once while my method is checking the user object a number of times. Eventually the test will just check that the cookie has been set so I can change the User stub to:

httpContextService.Stub(c => c.User).Return(user).Repeat.Any();

view raw example3.cs hosted with ❤ by GitHub