From reading the docs and the source, it's not a proxy. It looks like it uses https://github.com/pretenderjs/pretender https://github.com/pretenderjs/pretender

From reading the docs and the source, it's not a proxy. It looks like it uses https://github.com/pretenderjs/pretender https://github.com/pretenderjs/pretender , which overwrites the original `XmlHttpRequest` and `fetch` functions in the browser to intercept any attempts to make AJAX requests. It then makes your attempted request with its own internal routing definitions, and returns the responses you defined.