Code Coverage in Gerrit

Have you ever wanted to know if your CL has enough code coverage? You can see uncovered lines in Gerrit, which can help you figure out if your CL or the CL you're reviewing needs more/better tests.

To generate code coverage data for your CL, manually trigger the experimental coverage CQ builder: linux-coverage-rel:

choose_tryjobs linux_coverage_rel

Once the build finishes and code coverage data are processed successfully, look at the right column of the side by side diff view to see which lines are not covered:



Reporting problems

For any breakage report and feature requests, please file a bug.

Mailing list

For questions and general discussions, please join code-coverage group.


Why is the coverage CQ builder needs to be triggered manually?

We‘re still evaluating the stability of the code coverage pipeline, and once it’s proven to be stable, the experimental builder will be merged into one of the existing CQ builders, and at that time, the feature will be available by default.

Why is coverage not shown even though the try job finished successfully?

There are several possible reasons:

  • All the added/modified lines are covered.
  • A particular source file/test may not be available on a particular project or platform. As of now, only chromium/src project and Linux platform is supported.
  • There is a bug in the pipeline. Please file a bug to report the breakage.

How does it work?

Please refer to for how code coverage works in Chromium in general, and specifically, for per-CL coverage in Gerrit, the clang_code_coverage_wrapper is used to compile and instrument ONLY the source files that are affected by the CL and a chromium-coverage Gerrit plugin is used to annotate uncovered lines in Gerrit.