Backdoor APIs for QA testing - Good or Bad?

Are having APIs for the sake of QA testing a good or bad idea?

We're developing an application from scratch and we've been creating backdoor APIs to ease the jobs for the QAs. These backdoors do things many things like change the date of the server to emulate progression of time etc. I'm quite mixed on this. The number of these backdoors almost rival the real APIs that'll be used in Production.

Is this the recommended approach? The obvious benefit for this is that it makes the lives of the QA must easier. I can see many disadvantages with this also like maintaining the functionality of these test APIs, ensuring that these backdoor APIs are not exposed in production.

If others have used this approach, what are some good means to ensure that these APIs aren't exposed in production?

For those who are against this approach, are there alternatives to making the work for QA easier?

Thanks