## Summary
Suppress low-signal coverage Slack notifications that show +0.0% or
-0.0% deltas.
## Changes
- **What**: Add `MIN_DELTA` threshold (0.05%) so only meaningful
improvements trigger notifications. Only display rows for metrics that
actually improved (no more E2E row showing -0.0% alongside a real unit
improvement). Fix `formatDelta` to clamp near-zero values to `+0.0%`
instead of showing `-0.0%`.
- 4 of the first 6 notifications posted were noise (+0.0% deltas from
instrumentation jitter). With this change, only 2 of 6 would have been
posted — both showing real improvements.
## Review Focus
The `MIN_DELTA` value of 0.05 means any delta that rounds to ±0.0% at 1
decimal place is suppressed. This matches the display precision so users
never see +0.0% notifications.
┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-11283-fix-reduce-noise-in-coverage-Slack-notifications-3436d73d3650819ab3bcfebdb748ac8b)
by [Unito](https://www.unito.io)
## Summary
Adds a GitHub Actions workflow + TypeScript script that posts to Slack
when a merged PR improves unit or E2E test coverage.
## Changes
- **What**: New `coverage-slack-notify.yaml` workflow triggered on push
to main. Compares current coverage against previous baselines, generates
Slack Block Kit payload with progress bars and milestone celebrations,
posts to `#p-frontend-automated-testing`.
- **Script**: `scripts/coverage-slack-notify.ts` — parses lcov files,
computes deltas, detects milestone crossings (every 5%), builds Slack
payload. Pure functions exported for testability.
- **Tests**: 26 unit tests in `scripts/coverage-slack-notify.test.ts`
covering all pure functions including edge cases (malformed lcov, exact
boundaries, zero coverage).
### Security hardening
- All `${{ }}` expressions moved from `run:` blocks to `env:` variables
- `SLACK_BOT_TOKEN` passed via env var, not inline
- Unique heredoc delimiter (timestamp-based) prevents payload injection
- `parseInt` fallback (`|| 0`) guards against malformed lcov
- PR regex anchored to first line of commit message
### Robustness
- `continue-on-error: true` on Slack post step (outage does not fail the
job)
- Baseline save guarded by `steps.unit-tests.outcome == success`
(prevents corrupt baselines on test failure)
- Channel ID commented for maintainability
- Top-level `text` field added for Slack mobile push notifications
- Author linked to GitHub profile instead of bare `@username`
## Review Focus
- Workflow step ordering and conditional logic
- Security of expression handling and secret management
- Slack payload structure and Block Kit formatting
┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10977-feat-add-Slack-notification-workflow-for-coverage-improvements-33d6d73d3650819c8950f483c83f297c)
by [Unito](https://www.unito.io)
---------
Co-authored-by: GitHub Action <action@github.com>
