ChatGPT's API end-point for tesing of integration

Hi,

I’m developing an application which I want to integrate with ChatGPT. For testing of such integration I’m looking for an API end-point which will emulate real communications with ChatGPT but for free. I mean that what actually OpenAI’s back-end answers, doesn’t matter and it can be just “ok” or “error”.

Is there such end-point?

Sergio