Three years ago I left my job with VERY high salary because I was starting to burn out and took two months off.
From my experience, if you're burnt out or starting to burn out then leave, otherwise I recommend staying until you secure another job.
Regarding the situation, they want to delete the tests? Fine, you have git right? Replace it, and let everything set on fire, quietly enjoy the chaos and at some point revert the changes. Or don't, you're leaving anyway.