Is there a test API endpoint?

in Development
I have to develop some big changes in the way we sync our products, but our customer is already live. I'm not comfortable having to test my changes on his live data.
Is there a "mock" endpoint that I can use to test my integration?
3 comments
It would be best to use a test shop to test your integration.
Are API keys for test shops free?
We already have to use multiple API keys live because of the Lightspeed API limits, so that would mean our customer would have to purchase just as many (or at least several) additional API keys just for testing purposes.
Thank you for your response,
It should be possible for test shops to get 1 API key so you can test things out.