Schemathesis

Package

Generate property-based API tests from OpenAPI or GraphQL schemas

Price: Free, open source
Access: Target API credentials if required

About

Schemathesis generates and executes API tests from OpenAPI or GraphQL schemas, checking responses and exploring edge cases. It runs as a CLI or Python library against a reachable test endpoint. Generated operations can change test data; supply required endpoint credentials.

What you can do with it

Generate API tests from an OpenAPI schema instead of writing every case
Find server errors and schema violations with generated edge-case inputs
Test GraphQL endpoints and chained API workflows against a test environment

Get started

Install Schemathesis or run it with uvx
Use a test endpoint and its OpenAPI or GraphQL schema
Limit operations and pass test credentials where needed

Example

# Restrict generated tests to GET operations on your test API
uvx schemathesis run "$TEST_OPENAPI_URL" --include-method GET

Details

Hosting: Runs locally
Available in: Worldwide
Official SDKs: Python
MCP server: None