Practical ASP.NET

Unit Testing AJAX Calls to an ASP.NET MVC Controller

Sometimes what you want to test is how your Action method behaves when it's invoked through an AJAX call. Here's how to mock up that call using Moq.

In an earlier column on using Moq to create unit tests, I looked briefly at using the ControllerContext object to create a Session object that you could configure for testing.

Recently, though, I faced a different problem: I needed a unit test for an Action method that returned a different result depending on whether it was called through a normal HTTP request or through an AJAX request. As it turns out, this was just the start of a series of AJAX-related tests I needed to create, but this was the start of all my subsequent solutions.

The code in the Action method looks something like this:

If Request.IsAjaxRequest Then
  Return Json(Orders)
End If
Return View(Orders)

Obviously, I needed to mock the Request object so that I could set its IsAjaxRequest property:

Dim req As New Mock(Of HttpRequestBase)

However, to set the IsAjaxRequest property, ASP.NET MVC looks for an X-Requested-With HTTP header set to XMLHttpRequest on the Request object. So, I set up my mock Request object to return that value:

req.Setup(Function(r) r("X-Requested-With")).Returns("XMLHttpRequest")

I also needed to mock the HttpContext object because, under the hood, it's the HttpContext object that's responsible for returning the Request object used in my Controller. I mocked it and tied its Request property to my mock Request object:

Dim hct As New Mock(Of HttpContextBase)
hct.Setup(Function(h) h.Request).Returns(req.Object)

Now I could instantiate the HomeController class I wanted to test and set its ControllerContext object (the ControllerContext is responsible for managing the HttpContext object). I did that by instantiating a ControllerContext class, passing my mock HttpContext object, an empty RouteData table (because I didn't use it in my Action method), and my HomeController object. I shoved the resulting ControllerContext class into my HomeContoller object's ControllerContext property:

Dim hc As New HomeController
hc.ControllerContext = New ControllerContext(hct.Object, New RouteData(), hc)

Finally, I could call the Action method I wanted to test:

Dim ac As ActionResult
ac = hc.GetCustomerOrders(2)

It turned out, by the way, that this was just the start of various AJAX mockings I needed to create. However, from this point on, all I needed to do was keep extending my mock Request object.

About the Author

Peter Vogel is a system architect and principal in PH&V Information Services. PH&V provides full-stack consulting from UX design through object modeling to database design. Peter tweets about his VSM columns with the hashtag #vogelarticles. His blog posts on user experience design can be found at http://blog.learningtree.com/tag/ui/.

comments powered by Disqus

Featured

  • What's New in Visual Studio 2019 v16.5 Preview 2

    The second preview of Visual Studio 2019 v16.5 has arrived with improvements across the flagship IDE, including the core experience and different development areas such as C++, Python, web, mobile and so on.

  • C# Shows Strong in Tech Skills Reports

    Microsoft's C# programming language continues to show strong in tech industry skills reports, with the most recent examples coming from a skills testing company and a training company.

  • Color Shards

    Sharing Data and Splitting Components in Blazor

    ASP.NET Core Version 3.1 has at least two major changes that you'll want to take advantage of. Well, Peter thinks you will. Depending on your background, your response to one of them may be a resounding “meh.”

  • Architecture Small Graphic

    Microsoft Ships Preview SDK, Guidance for New Dual-Screen Mobile Era

    Microsoft announced a new SDK and developer guidance for dealing with the new dual-screen mobile era, ushered in by the advent of ultra-portable devices such as the Surface Duo.

  • How to Create a Machine Learning Decision Tree Classifier Using C#

    After earlier explaining how to compute disorder and split data in his exploration of machine learning decision tree classifiers, resident data scientist Dr. James McCaffrey of Microsoft Research now shows how to use the splitting and disorder code to create a working decision tree classifier.

.NET Insight

Sign up for our newsletter.

Terms and Privacy Policy consent

I agree to this site's Privacy Policy.

Upcoming Events