Global Changes Must Be Discussed With The Whole Team First

So you got tired of bad tests and decided it is a good idea to add some fuzz testing tool. Before you do add it in the main branch, you have to discuss it with your team.

It's mind-bogging that some people think something it's so good that they don't need to discuss with the whole team about it; they simply do. They don't seem to care that people have their workflows and changing something would break them. But hey, I've seen it so many times it is not even fun.

And let me clear here: You need to discuss it with the whole team, not just some of it (excluding people on vacations, 'cause you don't want to call them just to tell them something will change). Worse: Don't discuss only with those that will agree with you; you may not have seen all the problems those changes will inflict on the other devs workflows but, by bringing that with those that may not agree with you, you may gain some more insights on what could go wrong.

Also, focus on what would be the gains and the loses. "We'll get better tests, but you'll have to take a bit more care on the way you write tests" is a good explanation, specially if you show the changes people will have to do in future tests. Also also, notice that I said future tests: if you want to implement something new, you must be sure it won't require everyone getting out of their way to make your idea work -- don't make people rewrite tests 'cause they will break; don't make the other devs reformat their code 'cause you decided, alone, to add a linter to your CI with your own rules; don't make people worry about unwritten tests 'cause you decided it would be a good idea to add a code formatting tool and that would make your coverage tool think they are changing some unrelated piece of code that wasn't untested before.

Don't be a jerk thinking you know more than your whole team.