At my $job-2, my "dotted-line manager" got angry at me because I was spending time writing tests instead of implementing the feature he wanted me to implement. I completed both the tests and the feature one day before the deadline, and you've probably already guessed what happened on the deadline day: the specification changed. Without the tests, I would have been lost. It was pretty easy to fix the tests, and with the tests for the new specification, I was able to fix the code, too, and be confident that the change was correct. YMMV, but for me it was eye-opening.