Unit Testing Controller Actions that call IsAjaxRequest()

Some of my controller actions need to respond wi开发者_运维问答th different ViewResults depending whether or not they were called by an AJAX request. Currently, I'm using the IsAjaxRequest() method to check for this. When this method is called during a unit test, it throws an ArgumentNullException because the HTTP context is missing.

Is there a way to mock/fake this call? Or is this a sign I should be checking for an AJAX request another way?

Would it help if you provide a Test Double for the HTTP Context?

This can be done like this:

var httpCtxStub = new Mock<HttpContextBase>();

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

sut.ControllerContext = controllerCtx;

where sut represents the System Under Test (SUT), i.e. the Controller you wish to test.

This example uses Moq.

Using moq library in MVC test projects

[TestClass]
public class HomeControllerTest
{
    [TestMethod]
    public void Index()
    {
        // Arrange
        HomeController controller = new HomeController();
        controller.injectContext();
        // controller.injectContext(ajaxRequest: true);

        // Act
        ViewResult result = controller.Index() as ViewResult;

        // Assert
        Assert.IsNotNull(result);
    }
}


public static class MvcTestExtensions
{
    public static void injectContext(this ControllerBase controller, bool ajaxRequest = false)
    {
        var fakeContext = new Mock<ControllerContext>();
        fakeContext.Setup(r => r.HttpContext.Request["X-Requested-With"])
            .Returns(ajaxRequest ? "XMLHttpRequest" : "");
        controller.ControllerContext = fakeContext.Object;
    }
}