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name visual-regression
description Reference prompt for visual regression testing using playwright + cache-memory for baseline screenshot storage across pull requests

Visual Regression Testing

Use playwright for screenshots and cache-memory to persist baselines between PR runs.

Example Workflow

---
description: Capture screenshots on every PR and compare against cached baselines to detect visual regressions
on:
  pull_request:
    types: [opened, synchronize, reopened]
permissions:
  contents: read
  pull-requests: read
engine: copilot
tools:
  playwright:
    allowed_domains:
      - localhost
      - 127.0.0.1
  cache-memory:
    key: visual-regression-baselines-${{ github.event.pull_request.base.ref }}
    retention-days: 30
    allowed-extensions: [".png", ".json"]
  bash:
    - "mkdir *"
    - "cp *"
    - "diff *"
    - "date *"
safe-outputs:
  add-comment:
    max: 1
timeout-minutes: 30
---

Build and serve the app locally, then use Playwright to capture full-page screenshots of key pages into `/tmp/visual-regression/current/`.

Use filesystem-safe timestamps (no colons — colons break artifact uploads):
`date -u "+%Y-%m-%d-%H-%M-%S"`

If `/tmp/gh-aw/cache-memory/baselines/manifest.json` does not exist, copy screenshots there as new baselines and post: "Baselines initialized — N pages captured."

Otherwise compare each screenshot to its baseline. Post a comment summarizing: pages unchanged / pages with diffs. If nothing changed, use the `noop` safe-output.

Key Design Decisions

  • cache-memory key per base branch — scopes baselines to main, develop, etc.
  • Explicit baseline source — state whether baselines come from cache-memory, a generated artifact, or a branch directory; do not leave baseline origin implicit.
  • allowed_domains: [localhost, 127.0.0.1] — prevents SSRF; serve app locally
  • retention-days: 30 — beyond the default 7-day cache expiry
  • Filesystem-safe timestamps — YYYY-MM-DD-HH-MM-SS; colons break artifact filenames
  • Minimal permissions — all PR writes go through safe-outputs

Network-Minimization Reminders

  • Prefer local preview (localhost/127.0.0.1) over external preview environments.
  • If external previews are required, allowlist exact domains (no broad wildcards).
  • Enable network.node only when installing/building Node deps; scope to registries and preview hosts.
  • Keep Playwright navigation limited to app-under-test URLs.