Thread by @Fabiola31416

#UnitTesting and #TDD continue to deliver

Yesterday, I was fighting a pretty nasty bug, all the unit tests passed

I knew there was a corner case not covered by the unit tests but what was it?

Reviewing my assumptions, the key: hw was not exactly sync
Need to test for data 1/

Not aligned, I added new unit test for that assumption, of course the test failed

Now, I just needed to modify the code to make that test pass and not make the rest of the tests fail

The best part, i could work with very small and manageable arrays (instead of the 2GB array) 2/

Once all the tests passed, tested with hardware and everything just worked!

Let's see why this worked:
1) there were 35 unit tests that tested the "happy path" and some corner cases
2) I could confidently modify the code and know I would be alerted if I broke existing code
3/

Now I have 40 unit tests ready for the next corner case I didn't envision or when the customer changes the requirements

As usual, the real benefit of tests is found once you already have several unit tests, so, take the leap of faith and start creating some

4/

Next time you find a bug, before modifying code, create a unit test that needs to pass once the bug is fixed, then go fix the code and verify with the unit test that you indeed fixed it

And that is why I love Test Driven Development

Thanks for following along :)

5/5