Keith Dahlby has a good post on creating a fake SPContext.  Here’s the link and the code

NOTE: This is not production safe code – use at own risk…

http://solutionizing.net/2009/02/16/faking-spcontext/

public static SPContext FakeSPContext(SPWeb contextWeb)
{
  // Ensure HttpContext.Current
  if (HttpContext.Current == null)
  {
    HttpRequest request = new HttpRequest("", web.Url, "");
    HttpContext.Current = new HttpContext(request,
      new HttpResponse(TextWriter.Null));
  }

  // SPContext is based on SPControl.GetContextWeb(), which looks here
  if(HttpContext.Current.Items["HttpHandlerSPWeb"] == null)
    HttpContext.Current.Items["HttpHandlerSPWeb"] = web;

  return SPContext.Current;
}