Schemathesis is a property-based API testing tool that automatically generates test cases from OpenAPI and GraphQL schemas to find bugs and specification violations. It uses the Hypothesis property-based testing framework to generate diverse, edge-case-covering test inputs from schema constraints, detecting server crashes, response schema violations, validation bypasses, and stateful bugs in multi-step workflows.
Used by Netflix, SAP, Red Hat, IBM, and JetBrains.
Human URL: https://schemathesis.io
- Documentation
- Getting Started
- GitHub Repository
- PyPI Package
- Docker Image
- GitHub Action
- Changelog
- Blog
- Research Paper (ACM)
- Property-Based Testing — Generates thousands of test cases automatically from schema type constraints, format rules, enums, and patterns
- Schema-Driven Fuzzing — Inputs are constrained by schema definitions for targeted, meaningful fuzzing
- Response Validation — Checks status codes, response bodies, content types, and headers against OpenAPI declarations
- Stateful Testing — Follows OpenAPI Links to generate multi-step workflow tests
- Automatic Shrinking — Minimizes failing cases to smallest reproducible curl command
- CI/CD Native — GitHub Actions (
schemathesis/action@v2), GitLab CI, pytest integration
- OpenAPI 2.0 (Swagger), 3.0.x, 3.1.x
- GraphQL schemas (SDL and introspection)
pip install schemathesis
# or
uvx schemathesis run schema.json --url https://api.example.com- schemathesis-config-schema.json — JSON Schema for Schemathesis configuration
- schemathesis-config-structure.json — Document structure for .schemathesis.yml
- schemathesis-context.jsonld — Linked data context for Schemathesis vocabulary
- schemathesis-cli-test-example.json — CLI test run with output example
- schemathesis-vocabulary.yml — Domain vocabulary for Schemathesis concepts
Kin Lane — kin@apievangelist.com