.net mvc2 custom HtmlHelper extension unit testing

Question

My goal is to be able to unit test some custom HtmlHelper extensions - which use RenderPartial internally.

http://ox.no/posts/mocking-htmlhelper-in-asp-net-mvc-2-and-3-using-moq

I've tried using the method above to mock the HtmlHelper. However, I'm running into Null value exceptions. "Parameter name: view"

Anyone have any idea?? Thanks.

Below are the ideas of the code:

    [TestMethod]
    public void TestMethod1()
    {
        var helper = CreateHtmlHelper(new ViewDataDictionary());
        helper.RenderPartial("Test");  // supposingly this line is within a method to be tested
        Assert.AreEqual("test", helper.ViewContext.Writer.ToString());
    }


    public static HtmlHelper CreateHtmlHelper(ViewDataDictionary vd)
    {
        Mock<ViewContext> mockViewContext = new Mock<ViewContext>(
            new ControllerContext(
                new Mock<HttpContextBase>().Object,
                new RouteData(),
                new Mock<ControllerBase>().Object),
            new Mock<IView>().Object,
            vd,
            new TempDataDictionary(),
            new StringWriter());
        var mockViewDataContainer = new Mock<IViewDataContainer>();
        mockViewDataContainer.Setup(v => v.ViewData)
            .Returns(vd);
        return new HtmlHelper(mockViewContext.Object,
                                mockViewDataContainer.Object);
    }

Answer 1

Check this out...its a great article http://blogs.teamb.com/craigstuntz/2010/09/10/38638/

Answer 2

I was facing the same issue. When I pass the arguments to new Mock(), it is not setting them correctly. You need to set them up explicitly:

mockViewContext.Setup(v => v.View).Returns(new Mock<IView>().Object);
mockViewContext.Setup(v => v.ViewData).Returns(viewData);
mockViewContext.Setup(v => v.TempData).Returns(new TempDataDictionary());
mockViewContext.Setup(v => v.Writer).Returns(writer);