open-source-labs/Swell
Swell
Swell is an API development and testing client designed for interacting with modern network protocols, executing GraphQL operations, and running local mock servers. It provides a unified interface for connecting to endpoints served over HTTP/2, WebSockets, Server-Sent Events, gRPC, tRPC, and WebRTC, enabling live messaging, monitoring, and debugging.
The platform includes a concurrent load testing engine that spawns parallel worker threads to evaluate endpoint performance under heavy traffic, alongside a local mock server engine for simulating backend responses during frontend development. It features a schema introspection parser that analyses remote endpoint metadata to dynamically construct interactive query interfaces, and executes user-defined JavaScript snippets against incoming network payloads to programmatically validate data structures and status codes.
Workflows are organized through persistent workspace management, which serialises request collections and environment variables to local storage for offline use and file portability. Users can also run sequential request collections as automated test suites and manage testing workflows through local import and export utilities.
Features
- API and Protocol Testing - Provides a unified API testing client for modern streaming protocols like WebSockets, gRPC, and Server-Sent Events.
- API Testing Clients - Enables developers to send requests and monitor live responses across modern streaming protocols.
- WebSocket Testing Clients - Connects to WebSocket servers to send messages, stream real-time data, and inspect connection state.
- gRPC API Testing - Serves as a client for exploring, invoking, and monitoring gRPC service methods and streaming endpoints.
- Load Testing Tools - Spawns parallel worker threads to evaluate endpoint performance under heavy traffic loads.
- GraphQL Clients - Delivers a development environment for testing and debugging GraphQL queries, mutations, and subscriptions.
- Schema Introspection - Analyses remote endpoint metadata to dynamically construct interactive query interfaces and auto-complete inputs.
- Client Query Execution - Executes queries, mutations, subscriptions, and introspections against GraphQL endpoints with variable support.
- Frontend API Mocking - Runs a local mock server to simulate backend responses so frontend development continues independently.
- Network Protocol Testing - Connects to endpoints served over modern protocols like HTTP/2, WebSockets, Server-Sent Events, gRPC, tRPC, and WebRTC.
- Automated API Testing - Group multiple API requests into automated test suites and runs them sequentially to verify backend behavior.
- Automated Test Suites - Runs multiple API requests sequentially as an automated test suite by grouping them within a single workspace.
- HTTP Response Assertions - Executes user-defined JavaScript snippets against incoming network payloads to programmatically validate data structures.
- HTTP Load Testing - Subjects HTTP/2 and GraphQL endpoints to heavy traffic loads to evaluate backend server resilience.
- HTTP Mock Servers - Spins up embedded HTTP and socket servers locally to simulate backend endpoints for isolated testing.
- Concurrency Burst Testing - Spawns parallel worker threads to bombard target endpoints with heavy request volumes for performance evaluation.
- API Mocking Servers - Simulates backend endpoint responses locally to decouple frontend development from real infrastructure.
- GraphQL API Development - Executes queries, mutations, and subscriptions against GraphQL endpoints with variable support and schema introspection.
- Multi-Protocol Clients - Maintains modular transport drivers to normalise streaming and request-response lifecycles across diverse network protocols.
Star history
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