How Google Tests Software - Part Four

How Google Tests Software - Part Four

By James Whittaker

Crawl, walk, run.

One of the key ways Google achieves good results with fewer testers than many companies is that we rarely attempt to ship a large set of features at once. In fact, the exact opposite is often the goal: build the core of a product and release it the moment it is useful to as large a crowd as feasible, then get their feedback and iterate. This is what we did with Gmail, a product that kept its beta tag for four years. That tag was our warning to users that it was still being perfected. We removed the beta tag only when we reached our goal of 99.99% uptime for a real user’s email data. Obviously, quality is a work in progress!

It’s not as cowboy a process as I make it out to be. In fact, in order to make it to what we call the beta channel release, a product must go through a number of other channels and prove its worth. For Chrome, a product I spent my first two years at Google working on, multiple channels were used depending on our confidence in the product’s quality and the extent of feedback we were looking for. The sequence looked something like this:

Canary Channel is used for code we suspect isn’t fit for release. Like a canary in a coalmine, if it failed to survive then we had work to do. Canary channel builds are only for the ultra tolerant user running experiments and not depending on the application to get real work done.

Dev Channel is what developers use on their day-to-day work. All engineers on a product are expected to pick this build and use it for real work.

Test Channel is the build used for internal dog food and represents a candidate beta channel build given good sustained performance.

The Beta Channel or Release Channel builds are the first ones that get external exposure. A build only gets to the release channel after spending enough time in the prior channels that is gets a chance to prove itself against a barrage of both tests and real usage.

This crawl, walk, run approach gives us the chance to run tests and experiment on our applications early and obtain feedback from real human beings in addition to all the automation we run in each of these channels every day.

There are analytical benefits to this process as well. If a bug is found in the field a tester can create a test that reproduces it and run it against builds in each channel to determine if a fix has already been implemented.