This is a great talk by @KevlinHenney

When people write tests, they write less code.

Take a step back and try to look at the code from your colleagues perspective (at 24:00):

If I think it's difficult to use, what do the others think?

He says about the question if tests slow you down (at 1:33:01):

Yes, tests are your breaks. They will allow you to go faster, for the very reason they slow you down.