Question

I am testing code in a MVC HTML helper that throws an error when trying to get the application path:

//appropriate code that uses System.IO.Path to get directory that results in:
string path = "~\\Views\\directory\\subdirectory\\fileName.cshtml";
htmlHelper.Partial(path, model, viewData); //exception thrown here

The exception that is thrown is

System.Web.HttpException: The application relative virtual path ‘~/Views/directory/subdirectory/fileName.cshtml’ cannot be made absolute, because the path to the application is not known.

Following the advice of How to resolve issue with image path when testing HtmlHelper?
I have faked (using Moq):

• Request.Url to return a string
• Request.RawUrl to return a string
• Request.ApplicationPath to return a string
• Request.ServerVariables to return a null NameValueCollection
• Response.ApplyAppPathModifier(string virtualPath) to return a string

What else is needed to be able to allow this code to run in the context of a unit test run?
Or
What other approach should I be taking to render a Partial view on a dynamically built string?

Answer 1

As an alternative to mocking built-in .net classes, you can

public interface IPathProvider
{
    string GetAbsolutePath(string path);
}

public class PathProvider : IPathProvider
{
    private readonly HttpServerUtilityBase _server;

    public PathProvider(HttpServerUtilityBase server)
    {
        _server = server;
    }

    public string GetAbsolutePath(string path)
    {
        return _server.MapPath(path);
    }
}

Use the above class to get absolute paths.

And for For unit testing you can mock and inject an implementation of IPathProvider that would work in the unit testing environment.

–UPDATED CODE