Schemathesis
Property-based API testing from OpenAPI and GraphQL schemas
Microcks
API mocking and testing for OpenAPI, AsyncAPI, gRPC, GraphQL and SOAP
Hoverfly
Lightweight open source API simulation
Tavern
pytest plugin for API testing with YAML syntax
Dredd
Validates an API description against its implementation
Reqnroll
Cucumber-style BDD framework for .NET, successor of SpecFlow