Checking in fake private keys is fine for testing. Why is it bad, out of principle, just in case you check in bad private key? I think that's a bad argument bec

Checking in fake private keys is fine for testing. Why is it bad, out of principle, just in case you check in bad private key? I think that's a bad argument because there are a lot of benefits to being able to run end-to-end tests with some key.