Always ask for the reason before slating it :) Usually that's a single responsibility class: interface IGraphParser { Graph Parse(Request request);

Always ask for the reason before slating it :) Usually that's a single responsibility class: interface IGraphParser { Graph Parse(Request request); } Inject that into the caller via the container then you can mock the thing that calls it and just return a static Graph object, which you can't do with a simple extension method (which is why it sucks).