Is there hard evidence of the ROI of unit testing?

Question

Unit testing sounds great to me, but I\'m not sure I should spend any time really learning it unless I can convince others that is has significant value. I have to convince

Answer 1

I take a different approach to this:

What assurance do you have that your code is correct? Or that it doesn't break assumption X when someone on your team changes func1()? Without unit tests keeping you 'honest', I'm not sure you have much assurance.

The notion of keeping tests updated is interesting. The tests themselves don't often have to change. I've got 3x the test code compared to the production code, and the test code has been changed very little. It is, however, what lets me sleep well at night and the thing that allows me to tell the customer that I have confidence that I can implement the Y functionality without breaking the system.

Perhaps in academia there is evidence, but I've never worked anywhere in the commercial world where anyone would pay for such a test. I can tell you, however, that it has worked well for me, took little time to get accustomed to the testing framework and writing test made me really think about my requirements and the design, far more than I ever did when working on teams that wrote no tests.

Here's where it pays for itself: 1) You have confidence in your code and 2) You catch problems earlier than you would otherwise. You don't have the QA guy say "hey, you didn't bother bounds-checking the xyz() function, did you? He doesn't get to find that bug because you found it a month ago. That is good for him, good for you, good for the company and good for the customer.

Clearly this is anecdotal, but it has worked wonders for me. Not sure I can provide you with spreadsheets, but my customer is happy and that is the end goal.