Asserting Redirect to Action

Question

When using ASP.Net Core 2 MVC and FluentAssertions.AspNetCore.Mvc, how do I assert that a controller redirected to an action?

For example, given the following controller action:

public IActionResult SomeAction() {
  return RedirectToAction("SomeOtherAction");
}

How would I write a test verifying the redirection?

I'm looking for something like:

[Fact]
public void SomeActionTest() {
  var controller = new SomeController();
  var result = controller.SomeAction();

  result.Should().BeRedirectedToRouteResult().WithAction("SomeOtherAction");
}

...except instead of BeRedirectedToRouteResult().WithAction("SomeOtherAction"), I'm looking to assert something like BeRedirectedToAction("SomeOtherAction").

Answer 1

I personally would do something like the following:

Creating a static class containing the extension method and assertion class, which has a method called BeRedirectAction and then can be used like the following:

    [Fact]
    public void ActionReturnsView_ExpectedRedirectToError_TypeMismatch()
    {
        var controller = new HomeController();

        var result = controller.Index();

        result.Should().BeRedirectAction(nameof(HomeController.Error));
    }

Extension Method + Assertion Class

Example Static class

public static class ActionResultAssertionExtensions
{
    public class ActionResultAssertions : ObjectAssertions
    {
        public new IActionResult Subject { get; }

        public ActionResultAssertions(IActionResult subject) : base(subject)
        {
            Subject = subject;
        }

        [CustomAssertion]
        public void BeRedirectAction(string actionName, string because= null, params object[] becauseArgs)
        {
            var redirectResult = AssertionExtensions.Should(Subject).BeOfType<RedirectToActionResult>().Which;

            var actual = redirectResult.ActionName;
            var expected = actionName;

            Execute.Assertion.ForCondition(actual == expected)
                .BecauseOf(because, becauseArgs)
                .FailWith("Expected {context} to redirect to {0} Action but it is redirecting to {1}", expected, actual);
        }
    }

    public static ActionResultAssertions Should(this IActionResult subject)
    {
        return new ActionResultAssertions(subject);
    }
}

Sample Tests

Type Mismatch Test

This is an example failure of when the result is not a redirect:

    [Fact]
    public void ActionReturnsView_ExpectedRedirectToError_TypeMismatch()
    {
        var controller = new HomeController();

        var result = controller.Index();

        result.Should().BeRedirectAction(nameof(HomeController.Error));
    }

Result:

Expected type to be Microsoft.AspNetCore.Mvc.RedirectToActionResult, but found Microsoft.AspNetCore.Mvc.ViewResult.

Success Test

This is an example of a passing test

    [Fact]
    public void ActionRedirectsToError_ExpectedRedirectToError_TestShouldPass()
    {
        var controller = new HomeController();

        var result = controller.RedirectToError();

        result.Should().BeRedirectAction(nameof(HomeController.Error));
    }

Different Action Test

This is an example of a test failure when it gets redirected to a different action:

    [Fact]
    public void ActionRedirectsToIndex_ExpectedRedirectToError_TestSHouldFailSayingDifferentActionName()
    {
        var controller = new HomeController();

        var result = controller.RedirectToIndex();

        result.Should().BeRedirectAction(nameof(HomeController.Error));
    }

Result:

Expected result to redirect to "Error" Action but it is redirecting to "Index"

N.B.

The above does not test for controller/area differences, or any other potential combinations, it just looks at the Action Name.