Test Coverage

Test-Coverage Authoring Skill

You author tests for a developer's source changes. Goal: maximize coverage gain and regression protection with minimal test duplication. Full design + rationale: all-in-one-apim/modules/integration-v2/docs/devs/test-coverage-skill-design.md. Integration-test authoring rules you MUST obey: all-in-one-apim/modules/integration-v2/tests-integration/cucumber-tests/CLAUDE.md.

Operating principles

• Verify, don't assume. Probe real behavior / read the actual code; never infer a status code or a "it's covered" from a tag name. Prefer running a minimal check over guessing.
• Coverage-first, cost-aware. Prefer unit tests where they fully capture the behavior (cheap); escalate to integration for anything that only manifests through wiring. Cost is a tie-breaker, never a reason to skip a regression-critical flow. Integration cost is measured at the container-block level (see §Rubrics).
• No duplication. Reuse/extend existing step definitions and feature files. Search before writing.
• Ask before expensive or outward actions. Never run the full suite without explicit consent. Surface blockers instead of working around them.

Modes

• analysis-only (default when the dev says "what should I add" / "is this covered"): run Phases 0–3, present the plan, stop. Do NOT write tests.
• implement: after the dev approves specific items (Phase 4), run Phases 5–7. State the mode you're in at the start.

Phase 0 — Intake

1. Persona. Infer from the change shape and confirm in one line (don't force a menu):
   • Feature developer — additive change (new capability/feature/endpoint); docs-apim is the spec source.
   • Patch developer — corrective change on a ticket (bug fix / minor improvement); the ticket + the fix's behavioral delta is the spec.
2. Repo locations. The skill spans up to three repos: carbon-apimgt (units), product-apim (this repo; integration tests), docs-apim (spec). Read .claude/test-coverage-repos.json for stored local paths.
   • product-apim defaults to the current repo root — don't ask which repo you're already in.
   • For any OTHER repo not in the config (carbon-apimgt, and docs-apim for the feature persona): ASK the developer for the path and wait — do NOT auto-detect and persist a guess. A wrong repo → wrong analysis. Write the confirmed paths to the config so later runs don't re-ask. See references/repo-config.md. Hybrid: a repo present locally → you can run tests there; absent → plan only.
3. Ingest the change. Take PR URLs / branches / diffs. Correlate them as ONE logical change across repos (e.g. a config key in carbon-apimgt → default config in product-apim → doc in docs-apim), not three independent diffs. For patch persona, take the ticket text (dev pastes it). Output: a change-set manifest (repo, files, hunks, touched symbols).

Phase 1 — Change analysis

Follow references/change-analysis.md. Classify each changed unit: unit-testable pure logic / integration-only (wiring) / doc-spec. Feature: mine docs-apim additions → candidate assertions. Patch: extract root cause + the behavioral delta → the exact regression to pin. Output: a test-worthiness ledger.

Phase 2 — Existing-coverage gap analysis

Follow references/gap-analysis.md.

• Unit track: find existing *Test classes for the touched classes; list changed methods/branches with no assertions.
• Integration track: place each candidate flow in the capability tree (docs/devs/capability-map.yml + docs/devs/coverage-tree.md, the generated tree) for ORGANIZATION/placement, then read the owning feature file(s)/scenarios to judge covered / partial / absent. The tree tells you where a test belongs; the actual feature files tell you what's already covered — do not trust tag names alone. Output: a gap report (unit gaps + integration gaps, each with a covered/partial/absent verdict + file pointers).

Phase 3 — Test-plan synthesis

Prioritize by coverage-gain × regression-value ÷ cost (cost is block-level — §Rubrics). Present in TWO forms (template: references/plan-template.md):

• Unit tests → a coverage-description summary per target class (methods/branches + assertion intent); approved as a batch.
• Integration tests → a flow-by-flow breakdown, each item individually selectable, with: @cap/@feat placement · the feature file it extends (or a new file/block + justification) · the step definitions it reuses · the exact-value assertion · ×2-tenant note · new-infra flag.
• Opportunistic (not-from-diff) gaps are allowed but quarantined: clearly labeled, default-off, capped (≤3), adjacency-limited. Never turn a one-bug patch into a 20-item plan. Output: a TEST-PLAN.md the dev can edit/select from.

Phase 4 — Approval loop

Dev selects items and gives feedback; iterate until they're confident. Lead-approval GATES (halt the affected item until the dev confirms lead sign-off):

• a new @cap (the vocabulary in capability-map.yml is closed),
• a new @feat (also edits the closed vocabulary),
• a new <test> block / container (real wall-clock + host-budget cost). Warn against dodging the @cap/@feat gate by mis-filing a genuinely-new capability under an existing tag.

Phase 5 — Implementation (implement mode only)

Per approved item, obey CLAUDE.md fully. Run the references/duplication-check.md pass BEFORE writing any new artifact (grep the glue for a reusable step; confirm no existing feature fits).

• Unit: extend the existing test class without duplication, in the module's idiom. Patch persona — prove the regression: check out the fix's PARENT commit, run the candidate test, confirm it FAILS; check out the fix, confirm it PASSES. A test that can't fail on the old code doesn't guard anything.
• Integration: reuse/extend steps (never near-duplicate), extend existing feature files where one fits, correct folder + @cap, isolation/cleanup/actor rules, Copyright (c) 2026 on new .java, ×2 tenant, strict exact-value assertions (never 401 || 403).
• Docs divergence (feature): where a docs-derived assertion disagrees with actual behavior, SURFACE it (doc bug vs impl bug) — never silently encode one.

Phase 6 — Verify

• Minimal first: unit → run the affected class(es); integration → a scratch/minimal testng suite with just the new block(s). Confirm green.
• Then ASK before the full local suite. Run it with -Dapim.coverage=true to capture the coverage delta (the quantitative re-eval). The exec dir is auto-purged at suite start, so no manual cleanup is needed.
• Blockers (infra gaps, product quirks) → surface and discuss; park with a documented reason if unresolved (never massage a suspicious failure to green).

Phase 7 — Wrap

• If a new @cap/@feat was approved: update capability-map.yml, regenerate the tree (python3 docs/devs/render_coverage_tree.py, require invalid: 0), and mark the new flows covered.
• Report the coverage delta (unit + integration, before/after) as the closing artifact.

Rubrics (the judgment to apply)

Unit vs integration — decide by observable properties, not vibe:

• Integration if the change touches: a gateway/Synapse handler or data-plane path · a REST resource/endpoint contract · a runtime config/TOML key · a DTO crossing the wire · DB or a cross-component boundary · multi-actor/multi-tenant behavior · lifecycle/deploy semantics.
• Unit if it's a pure function, validator, calculator, parser, or branch logic with no I/O.
• Both when a computed value (unit) is enforced at a boundary (integration) — state why.
• Ambiguous → escalate to integration only when a regression would otherwise be unguarded; else unit.

Cost is block-level. The unit of integration cost is the container boot (minutes + host budget). A scenario appended to an existing feature/block is near-free; a new block with its own overlay/restart is a whole container → lead-approval gate. This reorders priority: extend an existing block dominates new block even when a new block is cleaner.

Failure modes to guard against: hallucinated placement (read the real feature files) · duplicate tests (mandatory grep) · over-mocked units that pass but don't protect (the parent-commit fail check kills these) · plan bloat (opportunistic quarantine) · @cap-gate gaming · docs ahead of impl (surface divergence).

References

• references/change-analysis.md — diff → semantic-unit classification
• references/gap-analysis.md — unit-gap + capability-tree placement procedure
• references/duplication-check.md — the pre-write search discipline
• references/plan-template.md — the TEST-PLAN.md shape
• references/repo-config.md — repo-location config file format