Backup MS SQL AG on a non-production environment
So as a preface for this answer, please consider the following points:


If your system is meant to be HIGHLY AVAILABLE, what are your plans for inevitable down-time and data loss? Will the time taken to recover this environment mean it will simply be faster to keep backups?
If your system is simply a copy of production, why are you not mirroring your backup jobs on that system?


The above may highlight why you do in fact want to set up proper backup jobs. This said, here's a really bad idea™.

BACKUP LOG [DBName] TO DISK = N'nul';
BACKUP DATABASE [DBName] TO DISK = N'nul';


This uses the nul device to stream a backup into nothingness. It should take a similar time to how long the read phase of the backup takes.

N.B. The above should not go anywhere near any production systems - you could end up losing data, and your job. The backups taken using this code (and therefore your backup chain) are not recoverable in any way.