Fixture
Show HN: Flawd is mutation testing for the AI era
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What is Fixture?
Flawd is a mutation testing tool that plants small, realistic bugs into covered code lines and checks whether test suites catch them. It identifies blind spots in test assertions and integrates with AI coding agents to automatically generate missing tests via an agentic handoff mechanism.
Fixture pricing
Pricing model: Freemium
Free 14-day evaluation (no credit card); commercial entitlement required after trial; specific pricing not disclosed
Fixture pros
- Supports 5 languages (JavaScript, TypeScript, Python, Go, Rust) with unified tree-sitter parsing; no per-ecosystem plugins required
- Agentic handoff (flawd handoff) packages survivor data for AI agents to automatically write missing tests
- Docker isolation ensures reproducible runs, safe parallelism, and no side effects on the working tree
- Local-first with no cloud backend; integrates into commit loops and CI with incremental SQLite caching
Fixture cons
- Requires Docker; only runs on platforms with Docker support
- Binary access limited during pre-GA; evaluation request required; commercial entitlement needed after free trial
- Mutation testing is computationally intensive; may take significant time for large test suites
Frequently asked questions about Fixture
What is mutation testing?
A method to measure test quality by injecting small bugs (mutants) into covered code lines and checking if tests catch them. Tests that miss mutants reveal blind spots in test logic and assertions.
What languages does Flawd support?
JavaScript, TypeScript, Python, Go, and Rust using tree-sitter parsing without per-ecosystem plugins.
Does Flawd require a cloud service?
No. Flawd is a self-contained binary that runs entirely locally on your machine or in CI pipelines; no cloud backend required.
Can Flawd integrate into CI/CD?
Yes. flawd ci scopes mutations to PR diffs, applies configurable mutation score thresholds to gate builds, and outputs SARIF for GitHub Code Scanning.