Enhance pick_experiment.cjs step summary with description and issue link

[Copilot]

The pick_experiment.cjs step summary only surfaced variant assignment counts, leaving engineers to dig into workflow YAML to understand experiment purpose and tracking context.

Changes

• actions/setup/js/pick_experiment.cjs: Extended writeSummary to append a ### Experiment Details section when any experiment declares description or issue metadata. Per experiment: bold name, > {description} blockquote, and Tracking issue: [#N](https://github.com/{repo}/issues/N) link (via GITHUB_REPOSITORY env var; falls back to plain #N if unset). No output change for bare-array experiments — fully backward-compatible.

• actions/setup/js/pick_experiment.test.cjs: Five new tests covering description-only, issue-only, both fields, legacy bare-array (no extras emitted), and missing-GITHUB_REPOSITORY fallback.

Example output (object-form experiment with both fields)

## 🧪 A/B Experiment Assignments

| Experiment | Selected Variant | All Variants | Cumulative Counts |
| --- | --- | --- | --- |
| `style` | **concise** | concise, verbose | concise: 3, verbose: 2 |

### Experiment Details

**style**

> Controls response verbosity for the summarization workflow.

Tracking issue: [#42](https://github.com/github/gh-aw/issues/42)

[Copilot]

Pull request overview

Enhances the pick_experiment.cjs step summary so engineers can see experiment purpose and tracking context (description + tracking issue link) directly in the workflow run summary.

Changes:

• Extend writeSummary to optionally append an “Experiment Details” section with description (blockquote) and a tracking issue link derived from GITHUB_REPOSITORY.
• Add unit tests covering description-only, issue-only, both fields, legacy bare-array behavior, and missing-GITHUB_REPOSITORY fallback.

Show a summary per file

File	Description
actions/setup/js/pick_experiment.cjs	Appends optional experiment metadata (description + issue link) to the step summary.
actions/setup/js/pick_experiment.test.cjs	Adds tests validating the new summary rendering and backward compatibility.

Copilot's findings

Tip

Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

• Files reviewed: 2/2 changed files
• Comments generated: 1

[github-actions]

🧪 Test Quality Sentinel Report

Test Quality Score: 72/100

⚠️ Acceptable — with suggestions

Metric	Value
New/modified tests analyzed	5
✅ Design tests (behavioral contracts)	5 (100%)
⚠️ Implementation tests (low value)	0 (0%)
Tests with error/edge cases	2 (40%)
Duplicate test clusters	0
Test inflation detected	✅ Yes (78 test lines / 28 production lines = 2.79:1, threshold 2:1)
🚨 Coding-guideline violations	None

---

Test Classification Details

View all 5 test classifications

Test	File	Classification	Issues Detected
includes description as blockquote in step summary when description field is set	actions/setup/js/pick_experiment.test.cjs	✅ Design	Happy-path only; no edge cases
includes tracking issue link in step summary when issue field is set	actions/setup/js/pick_experiment.test.cjs	✅ Design	Happy-path only; no edge cases
includes both description and issue link when both fields are set	actions/setup/js/pick_experiment.test.cjs	✅ Design	Happy-path only; combination of the above two
does not include description or issue extras for legacy bare-array experiments	actions/setup/js/pick_experiment.test.cjs	✅ Design	Negative assertion; covers backward-compat invariant
renders issue number without link when GITHUB_REPOSITORY is not set	actions/setup/js/pick_experiment.test.cjs	✅ Design	Edge case: missing env var graceful degradation

---

Flagged Tests — Suggestions for Improvement

No tests were classified as implementation tests. The following are improvement suggestions rather than blocking issues:

⚠️ Test inflation: 78 test lines added for 28 production lines (ratio 2.79:1)

Threshold: 2:1
Note: The production change was focused (one if block in writeSummary), but 5 new tests cover it from multiple angles. The tests are individually high-value — this flag reflects proportionality, not test quality. Consider whether tests 1 & 2 could be folded into test 3 (the combination test) to reduce redundancy.

💡 includes both description and issue link when both fields are set

Classification: Design test — but partially overlaps with tests 1 and 2.
Suggestion: This test is the strongest of the three description/issue tests since it verifies both fields interact correctly. The standalone "description only" and "issue only" tests are still valuable to pinpoint which field fails in isolation. No changes required.

💡 Missing assertion messages

The new expect(rawCall).toContain(...) calls lack a descriptive message argument (e.g. expect(rawCall).toContain("...", "description should appear as blockquote")). While this is not a hard violation in vitest, adding messages makes failure output more readable. Low priority.

---

Language Support

Tests analyzed:

• 🐹 Go (*_test.go): 0 tests — no Go test files modified in this PR
• 🟨 JavaScript (*.test.cjs): 5 tests (vitest)

---

Verdict

✅ Check passed. 0% of new tests are implementation tests (threshold: 30%). All 5 new tests verify observable behavioral contracts of the writeSummary function — specifically the rendering of description and issue fields into the GitHub Actions step summary. The minor inflation flag (2.79:1 ratio) does not block the merge; the tests are well-written and genuinely catch behavioral regressions.

---

📖 Understanding Test Classifications

Design Tests (High Value) verify what the system does:

• Assert on observable outputs, return values, or state changes
• Cover error paths and boundary conditions
• Would catch a behavioral regression if deleted
• Remain valid even after internal refactoring

Implementation Tests (Low Value) verify how the system does it:

• Assert on internal function calls (mocking internals)
• Only test the happy path with typical inputs
• Break during legitimate refactoring even when behavior is correct
• Give false assurance: they pass even when the system is wrong

Goal: Shift toward tests that describe the system's behavioral contract — the promises it makes to its users and collaborators.

References:

• §25234002548

🧪 Test quality analysis by Test Quality Sentinel · ● 694.4K · ◷

[github-actions]

✅ Test Quality Sentinel: 72/100. Test quality is acceptable — 0% of new tests are implementation tests (threshold: 30%). All 5 new tests verify observable behavioral contracts.