Unit Testing JsonResult in MVC

Unit testing ActionResults is fairly easy yet JsonResults can pose a problem. I’ve seen a few ways to do this and they just seemed like “too much” to me. So here’s a way that I’ve devised that works very well. Its sort of has a “hack” feel to it, but it works perfectly.

Controller Action:

public JsonResult AddContent(string content, string contentName)
{
    var isExistingContent = false;
    var wasAdded = false; 

    if (_service.IsNewContent(contentName))
    {
        _service.AddNewContent(content, contentName);
        isExistingContent = false; 
        wasAdded = true; 
    }
    // do some other logic, etc 
    
    
    return Json(new {isExisting = isExistingContent, added = wasAdded});
}

If you want to test the JsonResult that is coming back then we need a way to grab it. Since its an anonymous type it makes things a bit more tricky.

Here’s how to test it:

 [Test]
public void The_controller_should_be_able_to_add_new_content()
{
    // Arrange 
    _mockService.Expect(x => x.IsNewContent("foo")).Return(false);
    _mockService.Expect(x => x.AddNewContent("blah", "fooey")).IgnoreArguments(); 

    // Act
    var result = _controller.AddContent("fresh data", "foo");

    // Assert
    var wrapper = new System.Web.Routing.RouteValueDictionary(result.Data); // Magic black box
    Assert.That(wrapper["isExisting"], Is.False);
    Assert.That(wrapper["added"], Is.True);
   
}

We can cast the anon type to a RouteValueDictionary and then test off of the keys. Blammo. Simple.