Writing tests takes time, now. It also takes time to keep tests up to date and passing. It is code which must be maintained. So it's a tax you pay now and forever.

But, they can win you back time, later, when you debug to fix a problem, refactor with less fear that you might break something, deploy with more confidence and so on.... It can be a well paid tax, if you do it with discipline and focus! It doesn't work when the poor developer does it with blindness and resistance! He feels like the government (project manager) is robbing him with some stupid tax