How to resolve issue with image path when testing HtmlHelper?

Question

I came across an issue when I was testing my HTML Helper. Basically I\'m creating a grid with loads of rows, columns and different types of data in it. In the header there i

Answer 1

You can just use this overload:

var imgPath = VirtualPathUtility.ToAbsolute("~/Images/SortingArrowUp.png", 
    context.Request.ApplicationPath);

This is what UrlHelper.GenerateContentUrl uses internally, and you only need to mock ApplicationPath.

Answer 2

The correct way is to call UrlHelper.GenerateContentUrl instead of VirtualPathUtility. In your helper code you would do something like this:

MvcHtmlString MyHelper(this HtmlHelper helper, ...) {
  // other code
  var imgPath = UrlHelper.GenerateContentUrl("~/Images/SortingArrowUp.png",
                                             helper.ViewContext.HttpContext);
  // other code
}

When unit testing you will have to pass in correctly mocked context objects. You need to mock HttpContext.Request.ApplicationPath - return some dummy app path, HttpContext.Response.ApplyAppPathModifier() - do nothing, HttpContext.Request.ServerVariables - return null, HttpContext.Request.Path and HttpContext.Request.RawUrl - return some value that makes sense.