rebuild-test-image

name	rebuild-test-image
description	"

Before You Start

• Dockerfile.test — the test image definition
• .github/workflows/docker-test-image.yml — fires only on Dockerfile.test path changes on main
• Makefile — test-image target
• .github/workflows/test.yml — pulls the image from GHCR on every CI run

Steps

1. Edit Dockerfile.test

Make the needed changes. Common scenarios:

Pinning bats helpers to a specific version (recommended — currently unpinned and cloned from HEAD):

# Before (broken — HEAD can have breaking changes):
RUN git clone https://github.com/bats-core/bats-support.git

# After (pinned to a specific tag):
RUN git clone --branch v1.11.1 --depth 1 https://github.com/bats-core/bats-support.git

Adding a system tool:

RUN apt-get update && apt-get install -y --no-install-recommends \
    your-tool \
    && rm -rf /var/lib/apt/lists/*

2. Build locally

make test-image

This builds and tags the image as ghcr.io/joelbarmettleruzh/ultrainit-test:latest locally.

3. Run the full test suite against the new image

make test-all

Verify all tests pass with the new image before pushing.

4. Push to main

Commit and push Dockerfile.test to main. The .github/workflows/docker-test-image.yml workflow triggers only when Dockerfile.test changes on main.

git add Dockerfile.test
git commit -m "chore: pin bats-support to v1.11.1 in test image"
git push origin main

5. Monitor the GHCR image rebuild

gh run list --workflow=docker-test-image.yml
gh run watch

The workflow pushes to ghcr.io/joelbarmettleruzh/ultrainit-test:latest. No version tag — always :latest.

6. Verify the next CI run uses the new image

Trigger a test run (push any change) and verify test.yml pulls successfully:

gh run list --workflow=test.yml

Verify

make test-image && make test-all

Common Mistakes

1. No concurrency control — docker-test-image.yml has no concurrency group. Two simultaneous pushes to main with Dockerfile.test changes race to push :latest. If this becomes a problem, add concurrency: { group: docker-build, cancel-in-progress: true } to the workflow.

2. GHCR image doesn't exist yet on a fresh fork — test.yml will hang or fail on image pull. Run make test-image and push first.

3. Editing Dockerfile.test on a branch, not main — docker-test-image.yml only fires on main. A branch change won't rebuild the GHCR image. Test locally with make test-image and verify before merging.