Test Build Decision

When updating build-decision, it’s a good idea to test your changes before pushing them live. There are two approaches: a quick local dry-run against real hg.mozilla.org, and a full end-to-end test using a Taskcluster hook.

Local dry-run

This validates the build-decision code path against real hg.mozilla.org without deploying a Docker image. It exercises push info fetching, file list collection, .taskcluster.yml fetching, and task rendering — but does not submit a task.

1. Find a recent revision from mozilla-central:

   curl -sL 'https://hg.mozilla.org/mozilla-central/json-pushes?version=2&full=1&tipsonly=1'
   

2. Set the PULSE_MESSAGE environment variable with the revision:

   export PULSE_MESSAGE='{"payload": {"type": "changegroup.1", "data": {"pushlog_pushes": [{"pushid": 1}], "heads": ["<revision>"]}}}'
   

3. Run build-decision hg-push with --dry-run:

   TASKCLUSTER_ROOT_URL=https://firefox-ci-tc.services.mozilla.com/ \
   uv run --package build-decision build-decision hg-push \
     --repo-url https://hg.mozilla.org/mozilla-central \
     --project mozilla-central \
     --level 3 \
     --repository-type hg \
     --trust-domain gecko \
     --dry-run
   

The rendered Decision task JSON will be logged. If you see Decision Task: {...} in the output, the test has passed.

Test with the hook

This tests the full Docker image end-to-end using the test-build-decision hook in Taskcluster.

1. Push a PR to fxci-config. Wait for the docker-image-build-decision CI task to complete (visible in the GitHub checks UI).

2. Open the test-build-decision hook in Taskcluster web.

3. Edit the image field in the hook definition to reference the image built by the PR’s docker-image-build-decision task:

   {
     "type": "task-image",
     "taskId": "<docker-image-task-id>",
     "path": "public/image.tar.zst"
   }
   

   Save the hook.

4. Fire the hook manually.

You should see a new event for the triggered hook. If it successfully creates a Decision task, the test has passed!