api-testing

Hurl is a command line tool that runs HTTP requests defined in a simple plain text format.

Turn any OpenAPI2/3 and Postman Collection file into an API server with mocking, transformations and validations.

Restfox

Open-source API client with a native C++ load-testing engine - Postman-style requests and k6-level load tests in one local app.

Interactive multi-protocol API browser and CLI for .NET — gRPC, REST, GraphQL, SignalR, MCP, SSE, WebSocket, MQTT, Socket.IO, OData, Surgewave, Kafka, DIS, UDP.