| name | fuzz-harness-builder |
| description | Use when creating, adapting, reviewing, or debugging JS/TS fuzzers, corpus fixtures, replay files, shrinkers, repro writers, or deterministic random test harnesses. |
Fuzz Harness Builder
Fuzzers should produce useful failures, not just random load.
Required Properties
- Deterministic seed:
--seed.
- Bounded run size:
--cases, and target-specific caps where needed.
- Replayable failure:
--replay or --write-repro.
- Stable oracle: compare against a target-owned contract from docs, tests, source, or fetched material.
- Corpus promotion path: failures become checked-in fixture cases.
- Source traceability: corpus ideas from external projects cite the source-pass note or fetch manifest.
Workflow
- Identify the contract from the target project.
- Generate valid values first, then mutate them according to the target contract.
- Add or adapt a template:
npx evidence-kit add-fuzzer --name core --language js
- Replace
runSubject() with the project API under test.
- On failure, write a reduced JSON repro and add it to the corpus.
- When fuzzing ideas come from external sources, run
npm run research:list and cite the matching source note.
Reporting
Final reports should include command, seed, cases, any replay path, and whether corpus fixtures were added.
