Experienced Devs

yea but if we both aren't really keen on writing tests and I review you, it would be in my lazy ass' interest to 👍 without tests.

I think that instead of "forcing tests", you should instead focus on "proving quality." You think that works the way you thought? Cool. How do you know? What if they were to use 128 NUL bytes? Would it still do the right thing? Cool. How do you know?

Ensuring quality is a larger concept than simply writing tests, but writing tests is definitely part of it. I think if you aim higher and teach the provability of quality, then the better engineers will self-select by starting to write tests.

"If you want to build a ship, don't drum up people to collect wood and don't assign them tasks and work, but rather teach them to long for the endless immensity of the sea." — Antoine de Saint-Exupery

Additionally, if you're one person against the world, you're going to have a tough time. Build alliances. Partner with people who will reinforce the message. If you are the only one telling them something they don't like, they will shun you for it. But if you partner with allies who all have the same message, people are more likely to start to listen. It starts to become a community.

And if all else fails, prove the value of tests by going first. You can't force anyone to do anything. But you can start doing this yourself. At some point, if code gets called into question, you can look at the tests together to see what's covered and how that thing is supposed to work. It's all part of letting the robots do what the robots are good at, which frees you up to do the things that you're good at.