Bazel

A guide for generating Trunk-compatible test reports with Bazel

You can automatically detect and manage flaky tests in your Bazel projects by integrating with Trunk. This document explains how to configure Bazel to output compatible reports that can be uploaded to Trunk for analysis.

Checklist

By the end of this guide, you should achieve the following before proceeding to the next steps to configure your CI provider.

Generate a compatible test report
Configure the report file path or glob
Disable retries for better detection accuracy
Test uploads locally

After correctly generating reports following the above steps, you'll be ready to move on to the next steps to configure uploads in CI.

Generating Reports

Trunk can parse JSON serialized Build Event Protocol (BEP) files to detect flaky tests. You can run tests with Bazel in CI with the nobuild_event_json_file_path_conversion option to produce a serialized BEP file:

bazel test <TARGETS> \
    --nobuild_event_json_file_path_conversion

Report File Path

You can specify the path of the generated report through the build_event_json_file option:

bazel test <TARGETS> \
    --nobuild_event_json_file_path_conversion
    --build_event_json_file=build_events.json

Trunk can parse the build_events.json file to locate your test reports. You will still need to configure your test runners to output compatible reports, and you can refer to the guides for individual test frameworks.

Build Without the Bytes

If your CI environment is set up to build without the bytes, you will need the following flag to pull the reports from the remote execution engine:

--remote_download_regex='.*/test.xml'

Disable Retries

You need to disable automatic retries if you previously enabled them for more accurate detection results.

Disable retries if you're retrying tests using the --flaky_test_attempts command line option or retrying in your test runner.

Try It Locally

The Validate Command

You can validate your test reports using the Trunk CLI. If you don't have it installed already, you can install and run the validate command like this:

curl -fsSLO --retry 3 https://trunk.io/releases/trunk && chmod +x trunk
./trunk flakytests validate --junit-paths "./junit.xml"

This will not upload anything to Trunk. To improve detection accuracy, you should address all errors and warnings before proceeding to the next steps.

Test Upload

Before modifying your CI jobs to automatically upload test results to Trunk, try uploading a single test run manually.

You make an upload to Trunk using the following command:

curl -fsSLO --retry 3 https://trunk.io/releases/trunk && chmod +x trunk
./trunk flakytests upload --bazel-bep-path=build_events.json \
    --org-url-slug <TRUNK_ORG_SLUG> \
    --token <TRUNK_ORG_TOKEN>