Mock IUmbracoContextFactory

test.cs

private readonly IUmbracoContextFactory _context;
private readonly string _pluginPath;

public LicensingService(ILogger logger, IUmbracoContextFactory context) : base(logger)
{
    _context = context ?? throw new ArgumentNullException(nameof(context));
    _pluginPath = $"{IOHelper.ResolveUrl(SystemDirectories.AppPlugins).TrimEnd('/')}/plumber/";
}

public Tuple<string, string> GetLicenseAndKey() {
  using (var cref = _context.EnsureUmbracoContext())
  {
      // under test, with a mocked _context, HttpContext and Server are null (which is expected). I don't really want to mock all the way down,
      // because the context factory is a pretty large, complex object
      var keyPath = cref.UmbracoContext.HttpContext.Server.MapPath($"{_pluginPath}plumber.key");
      // instead, I think this would work fine, and remove the need for the factory entirely
      // HttpContextManager is mine, and can be mocked
      var licPath = HttpContextManager.Current.Server.MapPath($"{_pluginPath}plumber.lic");

      // other stuff happens here which is irrelevant to the mocking issue...
  }
}

Thanks Dennis, really appreciate your time. Might have to start nagging HQ to do make more ctors public