[tbranyen]

Have to disagree. I've found plenty of issues that affect real production users through the use of AB testing. Problems that were small enough to escape review, testing, and reporting, but large enough to be stat-sig. They always lead to a bug, or issue with test vs control.

I will always use AB testing for uncertain code in the future. I was skeptical when I first started writing AB tests, but they have proven their worth over and over again.

[ratww]

Sure, but that's not really A/B testing, those are more often called staged rollouts or progressive rollouts.

[tbranyen]

I'm talking about running week or month long tests with control and multi test cells containing new functionality, configuration, or code to determine the viability of a single or combination of changes by analyzing statistical output driven by p-value and pre-determined target metrics.

These types of experiments are extremely valuable in uncovering hard-to-find bugs, assuming you have sufficient logging and confidence around your metrics. They let you know a problem exists and roughly where it is in the product. From there you can drill down and investigate your source code until the discrepancy is found.