Schemathesis

Schemathesis is an open source tool that tests APIs by generating test cases from their schemas. It supports OpenAPI and GraphQL definitions and is released under the MIT license.

Schemathesis reads your API schema and creates many test inputs from the types and limits it describes. It sends those inputs to a running server and checks each response against what the schema says should happen. When it finds a failure, it reports the request, the response and a command that reproduces the problem. It can also chain several operations together to test workflows where one response feeds the next request.

• Generates tests from OpenAPI and GraphQL schemas
• Tries boundary values and type mismatches
• Checks status codes, headers and bodies against your spec
• Chains operations into multi-step stateful tests
• Runs from Python, Docker, GitHub Actions or GitLab CI

Backend teams that already maintain an OpenAPI or GraphQL schema and want more coverage without writing every case by hand. It also suits QA engineers who need repeatable API checks inside a pipeline.

Schemathesis is open source under the MIT license, so the code can be used and read freely. It runs from the command line, so the target API must be reachable from wherever the tests run. Results depend on the quality of the schema you give it, so an incomplete or inaccurate spec will limit what the tool can find.