Schemathesis
Schemathesis generates property-based tests from OpenAPI and GraphQL schemas to help engineers find API bugs.
What Schemathesis is
Schemathesis generates property-based tests from OpenAPI and GraphQL schemas to help engineers find API bugs. Its test cases probe boundary values, type mismatches, and constraint violations, and it checks API responses against the OpenAPI specification. For multi-step workflows, it can chain operations through links inferred from a schema. During a run, Schemathesis can learn validation rules, resource IDs, and authentication requirements from server responses and reuse them. Engineers can add Python checks for business rules. It supports OpenAPI 2.0, 3.0, 3.1, and 3.2, as well as GraphQL schemas. Authentication options include Bearer tokens, Basic authentication, and API keys, with environment variable substitution and Python hooks for dynamic flows. Integrations include a GitHub Action, Docker image, pip or uvx installation, and pytest. Reports can be exported as JUnit, VCR, HAR, NDJSON, JSON, and Allure; failures can also be saved with curl commands for replay. The tool is free, MIT-licensed, and self-hosted, with support for Linux, macOS, and Windows.
Good
- Generates cases for OpenAPI and GraphQL schemas.
- Supports stateful multi-step API workflows.
- Offers several report export formats.
- Free and MIT-licensed.
Watch out
- Deployment model is self-hosted.
- Technical support is directed through Discord.
Who it suits
Schemathesis is intended for engineers testing OpenAPI or GraphQL APIs and incorporating API checks into CI/CD. It may suit teams that want schema-generated tests and self-hosted deployment.
Verdict
Schemathesis combines schema-based test generation with response validation, adaptive behavior, and CI/CD integrations. It is a free self-hosted option for engineers working with OpenAPI or GraphQL APIs.
Plans and prices
From Schemathesis's own pricing page, checked 4 Oct 2026.
| Plan | Price | What it gives you |
|---|---|---|
| Schemathesis | Free | Open-source API testing tool; generates tests from OpenAPI and GraphQL schemas |
The facts
Each one read from Schemathesis's own pages, with the date it was checked.
What it does
- Adaptive testing
- During a run, it learns from server responses and reuses discovered validation rules, resource IDs, and authentication requirements.checked 4 Oct 2026
- Authentication
- It supports Bearer tokens, Basic authentication, and API keys, with environment variable substitution and Python hooks for dynamic flows.checked 4 Oct 2026
- Custom checks
- Users can add Python checks for business rules alongside built-in checks.checked 4 Oct 2026
- Integrations
- The maker lists a GitHub Action, Docker image, pip or uvx installation, and pytest integration.checked 4 Oct 2026
- Intended users
- The maker presents Schemathesis for engineers testing OpenAPI or GraphQL APIs and integrating API tests into CI/CD.checked 4 Oct 2026
- License
- The project repository states that Schemathesis is licensed under the MIT license.checked 4 Oct 2026
- Purpose
- Schemathesis generates property-based tests from OpenAPI and GraphQL schemas to find API bugs.checked 4 Oct 2026
- Reports
- It can export JUnit, VCR, HAR, NDJSON, JSON, and Allure reports, and save failures with curl commands for replay.checked 4 Oct 2026
- Response validation
- It validates API responses against the OpenAPI specification.checked 4 Oct 2026
- Security and privacy
- The privacy policy says the company uses commercially acceptable means to protect personal data but cannot guarantee absolute security.checked 4 Oct 2026
- Specifications
- It supports OpenAPI 2.0, 3.0, 3.1, and 3.2, plus GraphQL schemas.checked 4 Oct 2026
- Stateful testing
- It chains API operations into multi-step workflows using links inferred from the schema.checked 4 Oct 2026
- Support
- The maker directs users to Discord for technical support, configuration questions, bug reports, and integration examples.checked 4 Oct 2026
- Test generation
- It generates cases that probe boundary values, type mismatches, and constraint violations.checked 4 Oct 2026
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