Rendered from docs/process/obligations/0147-the-skills-fixture-suite-passes-on-an-empty-input-set-and-always-fails-in-a-clone-that-has-not-built-the-engine.md in the Headwater corpus. Every document on this half of the site is typed by the taxonomy the descriptor names: corpus.json.

The skills fixture suite passes on an empty input set, and always fails in a clone that has not built the engine

Context

Both defects surfaced while verifying pull request #328, which closed issue #309, and both predate that pull request rather than being caused by it. .claude/skills/fixtures.sh is the suite that checks the repository's own instruction files against the verbs they name, and it is the mechanism at issue here. Neither defect has a reader outside this repository, which is why it is self-audit rather than adopter-blocking.

Obligation

Three cases in .claude/skills/fixtures.sh count the verbs an instruction file names into a variable called counted. Each case then reports a pass message that interpolates counted without comparing it against anything. On a scratch tree with every SKILL.md and every .claude/agents/*.md file removed, one case reports ok 0 verbs named, and every one of them ships. The suite exits 0, with all four cases passed. A count that is never checked against a floor cannot distinguish a corpus with verbs from a corpus with none. The Rust suite already carries the fix as a pattern. engine/crates/cli/tests/verbs.rs asserts forms.len() > 20 before it compares. Its verb-index case uses BTreeSet equality, which an empty left side cannot satisfy unless the right side is empty too.

A second, unrelated defect fails the same suite in the opposite direction. .claude/agents/headwater-maintainer.md:26 cites engine/target/release/headwater as a repository path, inside a sentence that tells the reader to build it if absent. A link-resolution case in the suite reads that citation as a path that must exist. In any clone that has not compiled the engine, sh .claude/skills/fixtures.sh exits 1, with 21 cases passed, 1 failed, and 2 skipped. This is why the benefit of #328, that the verb case now runs without a built engine, stops at that one case. It never reaches the suite's own exit status.

Discharge

Closing this needs a guard before the comparison, in all three counted cases, matching the floor verbs.rs already asserts. It also needs one case that pins the guard. That case is an instruction-free scratch tree that exits non-zero and names the empty set in its message, rather than claiming everything shipped. The unbuilt-engine path needs the same treatment, as a skip rather than a failure. With that fix, sh .claude/skills/fixtures.sh exits 0 in a worktree that has never compiled the engine, and names its engine-dependent cases as skipped. A pull request that states the case count under both conditions, built and unbuilt, lets a later reader tell a skip from a silent pass. Eighteen further 2>&1 stream merges in the four fixture suites remain unaudited, and are out of scope for this record.