Unit Test a HtmlHelper in ASP.net MVC

Question

I have a HtmlHelper that returns the bootstrap selected class. I use this helper to apply the active state to my menu items.

Helper Code

public static string IsSelected(this HtmlHelper html, string controllers = "", string actions = "",
      string ccsClass = "selected")
{
  var viewContext = html.ViewContext;
  var isChildAction = viewContext.Controller.ControllerContext.IsChildAction;

  if (isChildAction)
  {
    viewContext = html.ViewContext.ParentActionViewContext;
  }

  var routeValues = viewContext.RouteData.Values;
  var currentController = routeValues["controller"].ToString();
  var currentAction = routeValues["action"].ToString();

  if (string.IsNullOrEmpty(controllers))
  {
    controllers = currentController;
  }

  if (string.IsNullOrEmpty(actions))
  {
    actions = currentAction;
  }

  var acceptedActions = actions.Trim().Split(',').Distinct().ToArray();
  var acceptedControllers = controllers.Trim().Split(',').Distinct().ToArray();

  return acceptedControllers.Contains(currentController) && acceptedActions.Contains(currentAction)
    ? ccsClass
    : string.Empty;
}

Testing Code

[Test]
public void WhenPassedControllerAndActionMatchContextReturnSelectedClass()
{
  var htmlHelper = CreateHtmlHelper(new ViewDataDictionary());
  var result = htmlHelper.IsSelected("performance", "search");

  Assert.AreEqual("selected", result);
}

public static HtmlHelper CreateHtmlHelper(ViewDataDictionary viewData)
{
  var mocks = new MockRepository();

  var controllerContext = mocks.DynamicMock<ControllerContext>(
    mocks.DynamicMock<HttpContextBase>(),
    new RouteData(),
    mocks.DynamicMock<ControllerBase>());

  var viewContext = new ViewContext(controllerContext, mocks.StrictMock<IView>(), viewData, new TempDataDictionary(), mocks.StrictMock<TextWriter>());

  //var mockViewContext = MockRepository.GenerateMock<ViewContext>();

  var mockViewDataContainer = mocks.DynamicMock<IViewDataContainer>();

  mockViewDataContainer.Expect(v => v.ViewData).Return(viewData);

  return new HtmlHelper(viewContext, mockViewDataContainer);
}

This is giving me an error. When I debug, I see that it is because ControllerContext is null on Line 5 of Helper code.

What would be the flexible, correct way of testing that code?

Sam · Accepted Answer · 2017-07-23 06:49:38Z

1

I've noticed that your are using rhino-mocks but it possible (and really easy) to solve your problem using Typemock Isolater by faking the dependencies of HtmlHelper as shown in the following example:

[TestMethod, Isolated]
public void WhenPassedControllerAndActionMatchContextReturnSelectedClass()
{
    var fakeHtmlHalper = Isolate.Fake.Dependencies<HtmlHelper>();
    var fakeViewContext = Isolate.GetFake<ViewContext>(fakeHtmlHalper);

    Isolate.WhenCalled(() => fakeViewContext.RouteData.Values["controller"]).WillReturn("performance");
    Isolate.WhenCalled(() => fakeViewContext.RouteData.Values["action"]).WillReturn("search");

    var result = fakeHtmlHalper.IsSelected("performance", "search");

    Assert.AreEqual("selected", result);

}

edited Jul 23, 2017 at 6:49

answered Jul 14, 2016 at 11:32

Sam

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