evidence-cluster

name	evidence-cluster
description	Use during code authoring + spec-review. Four practices bundled: (1) impact-aware test selection — run tests the changed files transitively reach, not just the ones you wrote; (2) anti-over-mock cue — no mocks outside test files; (3) complexity-delta gate during review — measure lines vs behaviour; (4) dual-reader ambiguity probe at SPEC review — second reviewer asks 'what does this permit/forbid that disagrees'.
license	internal-only
compatibility	["copilot","claude","bes-fleet"]
allowed-tools	[]
metadata	{"bes_provenance":{"origin":"internal","source_urls":[],"borrowed_from":[],"upstream_status":"not-applicable","last_audited":"2026-06-05T00:00:00.000Z","audit_cadence":"annual","adoption_status":"bes-native","security_review":"not-required","notes":"BES fleet-native skill."},"bes_tool_surface":{"scripts":"none","network":false,"dependencies":[],"secrets":[],"allowed_tools":[],"risk_notes":"No skill-local executable helper scripts."}}

Evidence Cluster

Four practices bundle here because they share one root: the artefact has to do the right thing, not just exist.

Use Cases

Invoke this skill when implementing a behaviour change (impact-aware tests + anti-over-mock), when reviewing a diff (complexity-delta gate), when reviewing a SPEC (dual-reader ambiguity probe).

The Four Practices

1. Impact-Aware Test Selection

Before declaring a behaviour change done:

• Identify the files you modified.
• Identify tests that transitively reach those files (import graph, not just sibling tests).
• Run THAT set, not just the tests you wrote.
• Cite the test run as a tool-receipt (execution-discipline-cluster cross-ref).
• If a predicate or contract gates behavior, execute it against the live filesystem/runtime before sign-off (file://specs/2026-06-22-fleet-sync-self-reconcile/SPEC_EVIDENCE.md SE-1).

For the BES fleet today the helpers are:

• bash .claude/hooks/tests/run-tests.sh — fleet hook impact.
• bash agents/scripts/<helper>.sh --self-test — per-helper impact.

2. Anti-Over-Mock Cue

Rules:

• NEVER add mock, jest.mock, vi.mock, MagicMock, etc. outside test files. Production code that needs a mockable seam should use dependency injection at module boundaries (per standards §U15 boundary validation).
• One mock per test, not many. Over-mocked tests test the mock, not the behaviour.
• If you find yourself mocking the database in more than half your tests the architecture is test-hostile. Surface it.

3. Complexity-Delta Gate (during review)

When reviewing a diff:

• Measure lines added vs behaviour added.
• If the code added is roughly an order of magnitude more than the behaviour warrants, flag as complexity-bloat. (Calibration: a ~200-line PR that adds one new public-API function is fine; ~2000 lines for that same one function is suspect — ~10x too much. Advisory cue, not a lint-enforced ratio.)
• Check imports added — every new dep is a long-lived liability; new deps without deps_added SPEC declaration are blocked by block-undeclared-deps.sh but advisory deps inside a node_modules churn warrant review.

4. Dual-Reader Ambiguity Probe (at SPEC review)

When cross-family reviewing a SPEC:

• Pick one normative claim per major section.
• Ask: "What behaviour does this permit / forbid that another reader might disagree on?"
• If the answer is "nothing" you've read it tightly; if the answer reveals interpretive surface, surface the ambiguity as a finding.

This is distinct from existing diff-review — the ambiguity probe targets the SPEC TEXT's interpretive surface, not the implementation.

Hard Rules

• Do not declare a behaviour change done without running impact-aware tests.
• Do not add mocks to non-test files.
• Do not let a PR whose size dwarfs its behaviour by ~an order of magnitude land unchallenged (see the complexity-delta cue above).
• Do not skip the ambiguity probe on Contract SPECs — Contract is the most-binding artefact type.

Cross-references

Host skills per practice: tdd (impact-aware selection), code-review (complexity-delta), spec-review (ambiguity probe), execution-discipline-cluster (tool receipts).