As someone who's about to assist a frontend team to implement testing against a backend I've developed (my first time doing something like this), I can see that mocking backend APIs is inherently tedious and error-prone. And I'm not confident that we have the resources to keep the mocked endpoints consistent with the real backend given the pressure to develop the "real product".

What are the downsides of of using a real API (e.g. dev environment) for automated testing?