1.5Trunk-Based Development in Detail

Trunk-based development takes GitHub Flow to its extreme. Feature branches live less than a day. Developers commit to main frequently, often multiple times per day.

main ──●●●●●●●●●●●●●●●●●●●●●● (continuous stream of small commits)
       ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑
       Very short-lived branches (hours, not days)

QA Implications for Trunk-Based Development

• Every commit must pass all tests: There is no stabilization period. The pipeline must be fast and reliable.
• Feature flags replace feature branches: Incomplete features are deployed behind flags, not on separate branches
• Testing shifts left dramatically: QA reviews requirements and writes tests before development starts, because there is no time to catch up later
• Flaky tests are existential threats: A flaky test that blocks main blocks the entire team. Fix flaky tests immediately.

When trunk-based development works:

• The team has high test automation maturity (>90% of tests automated)
• CI pipeline completes in under 10 minutes
• Feature flags are available and well-managed
• The team has strong code review discipline