Hello from Engineering Productivity! Once a month we highlight one of our projects to help the Mozilla community discover a useful tool or an interesting contribution opportunity.

This month’s project is mozregression!

Why is mozregression useful ?

mozregression helps to find regressions in Mozilla projects like Firefox or Firefox on Android. It downloads and runs the builds between two dates (or changesets) known to be good and bad, and lets you test each build to finally find by bisection the smallest possible range of changesets where the regression appears.

It does not build locally the application under test, instead, it uses pre-built files, making it fast and easy for everyone to look for the origin of a regression.

Examples:

# Search a Firefox regression in mozilla-central starting from 2016-01-01

mozregression -g 2016-01-01

# Firefox regression, on mozilla-aurora from 2015-09-01 to 2015-10-01

mozregression --repo aurora -g 2015-09-01 -b 2015-10-01

# Look for a regression in fennec (firefox for android)

mozregression --app fennec -g 2015-09-01 -b 2015-10-01

# regression on firefox in inbound, using debug builds and starting from known changesets

mozregression -b 6f4da397ac3c -g eb4dc9b5a928 -B debug --repo inbound

Note that a graphical interface exists also.

Where do I find mozregression ?

Start with:

• Documentation: http://mozilla.github.io/mozregression
• Source code: https://github.com/mozilla/mozregression
• Project overview: https://wiki.mozilla.org/Auto-tools/Projects/Mozregression

What are we working on ?

Currently mozregression is improving in multiple areas, among them:

• better graphical interface support
• JSShell support (to be used from autoBisect, https://github.com/MozillaSecurity/funfuzz/tree/master/autobisect-js)
• b2g bisection flow support (b2g devices regression hunting)

Contributions

William Lachance (:wlach) and myself (:parkouss) are the current maintainers of mozregression.

We welcome contributors! Mike Ling is helping the project for quite some time now, adding useful features and fixing various bugs – he’s currently working on providing ready to use binaries for Mac OS X. A big thanks Mike Ling for your contributions!

Also thanks to Saurabh Singhal and Wasif Hider, who are recent contributors on the graphical user interface.

If you want to contribute as a developer or help us on the documentation, please say hi on the #ateam irc channel!

Reporting bugs / new ideas

You can also help a lot by reporting bugs or new ideas! Please file bugs on bugzilla with the mozregression component:

https://bugzilla.mozilla.org/enter_bug.cgi?product=Testing&component=mozregression

mozregression’s bug list:

https://bugzilla.mozilla.org/buglist.cgi?component=mozregression&bug_status=__open__&product=Testing

For more information about all Engineering Productivity projects visit our wiki. If you’re interested in helping out, the A-Team bootcamp has resources for getting started.