Mocking HttpContext.server.MapPath in ASP.NET unit testing

I have working in unit testing in ASP.Net web application, now I have accessing my constructor in the model file to test which has Server.MapPath code for uploading my XMLfile, when try to testing this i get error, because the HttpContext is null so i have to mocking Server.MapPath.

I have searched lot but every samples given only for Asp.NET MVC but I have working in ASP.NET. so please help in ASP.NET to solve this issue.

My code is given below.

public class NugetPlatformModel
{
    public bool IsHavingLicense { get; set; }
    public List<PlatformProducts> PlatformProduct = new List<PlatformProducts>();
    public NugetPlatformModel()
    {
      var xmldoc = new XmlDocument();

       mldoc.Load(HttpContext.Current.Server.MapPath(@"~\Content\PlatformProducts.xml"));
    }
}

And my unit testing code

 [Test]
    public void Account_UnlicensedCustomerIdentity_IsStudioLicenseAndIshavinglicenseFalse()
    {

        //Act
        NugetPlatformModel nugetPlatformModel = new NugetPlatformModel();

        //Assert
        AssertEquals(false, nugetPlatformModel.IsHavingLicense);

    }