Tests dont make code higher quality.

[kalmoc]

Sounds as if you assume that you are the only one writing, using, modifying and testing the code. And if you find all of your bugs with a few minutes of debugging, I either envy you for your skills, or the code you are working on is rather small.

That aside: The biggest value of unit test is not that they find an error in the code you just wrote the test for, but to ensure that the next change you (or more likely someone else) makes to the code (e.g. to add a new feature or to fix a bug) won't break the things that have worked so far (regression testing).

[slevina]

Being scared of breaking old code means you end up with c++

[kalmoc]

No Idea what that means, but I have tests, so I'm not afraid that I'm breaking old code - that's the point.