If you are not unit testing your code, chances are you are not unit testing in your life.
If you aren’t unit testing, START now! At the very least, do some “manual” unit testing in your code. How can you do this? Well, try running your code on a very basic case. Then try a bit more complicated case. Then another, then another. If you are smart, you are saving these cases using a testing framework like NUnit. If not, well at least you can have some confidence when your manager comes that you tried it comprehensively and that it’s not going to crash on you while you are showing it to him, or even worse, in a demo to the team or to your big boss.
I recently ran into some problems in my life which I managed to solve amazingly well by doing “unit testing”...
First problem, my DVD burner was going awfully slow. I had some complex and messy setup including an external IDE card, two burners, two hard drives, and all I know is that at some point in time something went wrong and it started going really slow. What I don’t know, is how it happened.
Second problem, I was doing some video encoding/rendering, and for some reason it was doing something bizarre and the application VirtualDub kept looping over and over and would never end encoding the file. Again, I don’t know what happened.
How did I solve these problems?
UNIT TESTING!!
For the first problem of the DVD drive. I removed everything from my PC and set up a very basic system which included 1 HD, 1 Burner, etc.. Then when I found this wasn’t working, a quick check online and I resolved the issue which was incorrect DMA settings. It was trying to send all the data through the CPU (PIO mode) instead of directly to the burners, which was causing a massive slowdown. Once this worked, I quickly put together my system again, and checked each case (HD on same IDE channel as Burner, on separate IDE channel, and so on).
With the encoding problem, again, I was very confused, but by unit testing the situation, I was able to resolve it. How did I do that? I tried encoding on a different machine, reinstalled the software, etc, etc, and it was still having problems.
And finally when I started from scratch, I removed the batch encoding, I removed the DiVX processing, and so on, and then made each test pass. Once the test passed, I added another level of complexity, until finally I figured out that VirtualDub was looping infinitely because I had the “segment AVI file” option enabled. I don’t know why this was the problem, but by unit testing, I was able to resolve it.
Lesson to learn? Unit testing (if you can call it that) can really help you solve such issues. Start from the base case, and slowly work back towards what you need. After each case, write down the results.