Lesson 2.4: Regression Coverage
Difficulty: Beginner | Duration: 10 min | Prerequisites: Lesson 2.3
Overview
Once you record and assert, the next question is what have I actually covered? The Regression Coverage surface answers it per method: every discovered operation gets a small four-state chip so you can see, at a glance, where your recorded/tested traffic is fresh, stale, broken, or missing.
The four states
| Chip | Meaning |
|---|---|
| Recent | Covered by a recording/run within the freshness window — green, you're good. |
| Stale | Covered once, but not recently — the coverage exists but may not reflect the current contract. |
| Failing | The most recent run for this method failed an assertion — needs attention. |
| Uncovered | No recording/run touches this method at all — a blind spot. |
Coverage is computed from the workspace's recordings + Flow runs against the discovered surface, so the chip updates as you capture and run.
Steps
Drive the Harbor Combined sample (:5101/bowire).
1. See the chips in Discover
Open the sidebar. Each Harbor method carries a coverage chip. Straight after discovery — before you've recorded anything — most read Uncovered.
2. Cover a method
Record or run a Flow against one method (e.g. list docks). Its chip flips to Recent. Break an assertion on another method and run it — that one reads Failing.
3. Watch coverage decay
Coverage isn't just presence — it's freshness. A method covered long ago (outside the window) reads Stale, nudging you to re-capture against the current contract rather than trusting an old tape.
4. Work the blind spots
Filter/scan for Uncovered methods — that list is your regression backlog. The goal state: no Uncovered, no Failing, minimal Stale.
Key Takeaways
- Four states per method: recent · stale · failing · uncovered. A blind-spot map for your API surface.
- Coverage is freshness, not just presence. Stale coverage is flagged distinctly from missing coverage.
- Uncovered = your regression backlog. Capture/assert your way to green.
What's Next
Continue: → Lesson 2.5: Intercept rail — four postures