inessential by Brent Simmons

More Bug Math

When an app is under 100 bugs, you can start getting an idea for when it will be done.

The idea will be wrong, of course, but it’s still an idea.


I started keep tracking of the number of open bugs on Jan. 9, when we had 41 open bugs.

Now, 19 days later, we’re down to 12 open bugs.

That does not mean we’ve fixed just 29 bugs: we’ve probably fixed three times that many. And that’s because, this late in the game, we have a lot of testers and bug reports — and also because any bug fix could result in another bug. (Or two. Or three.)

However: the math says we’re netting 1.5 bugs fixed per day. In other words — despite the new bug reports — on average, every day we’re 1.5 bugs closer to shipping. That’s a pretty good rate of progress.

This tells me that we’ll be down to zero bugs in eight days. (We’ll fix a lot more than 12 bugs in those eight days, but in the end we’ll have no bugs left.)

Of course that’s not really true. This is app development, after all — a process so uncertain that it makes Chaos blush.

But still, it gives us an idea of when we might be done. Pretty confident it will be in 2020.