MockServer is a highly sophisticated, multi-protocol HTTP(S) mock server and proxy for testing, written in Java with Netty. It supports HTTP/1.1, HTTP/2, HTTP/3 (QUIC), gRPC, WebSockets, DNS, TCP, and binary protocols on a single port. The core engine provides expectation-based request matching, response generation, forwarding, proxying, recording, verification, and chaos engineering (latency, connection drops, error injection). It also includes built-in LLM mocking (OpenAI, Anthropic, Gemini, etc.), OIDC/OAuth2/SAML identity providers, SCIM provisioning, WASM custom rules, and drift detection. The repository is a monorepo containing the Java server, multi-language client libraries (Java, Node, Python, Ruby, Go, .NET, Rust, PHP), a React dashboard UI, IDE plugins (JetBrains, VS Code), Helm charts, Docker images, and extensive CI/CD pipelines via Buildkite. The architecture is modular with clear separation of concerns: core model/matcher/serialization in `mockserver-core`, Netty transport in `mockserver-netty`, language-specific clients in `mockserver-client-*`, and a React UI in `mockserver-ui`. The codebase demonstrates strong engineering practices including DTO patterns with Jackson serializers, a matcher hierarchy with compiled-once validators, bounded caches, constant-time equality checks, and extensive test coverage with integration tests across multiple environments.
Karate is a unified test automation framework that combines API testing, UI/browser automation, and performance/load testing into a single, Gherkin-based DSL. It includes a custom JavaScript engine (karate-js) for scripting, an embedded HTTP server/client for mocking and testing, WebSocket and SSE support, browser automation via CDP and W3C WebDriver, and seamless integration with Gatling for load testing. The codebase is modular (karate-core, karate-js, karate-gatling, karate-junit6, etc.) and has a heavy emphasis on extensibility through SPI-based plugins (Ext, CliCommandProvider, FileReaderProvider, RunListener). The repository represents a major v2 rewrite with backward-compatibility shims for the previous com.intuit.karate package. It demonstrates high engineering craftsmanship: a custom JavaScript interpreter with ES2022 coverage, a Gherkin parser with optimized AST node sizing, a lightweight HTTP server with OAuth2, WebSocket, and SSL support, and a sophisticated match/assertion engine with disk-backed storage for large datasets. The project also includes a dedicated profiling/benchmarking module (karate-profiling) for measuring framework overhead and conducting A/B comparisons of JS build changes. While primarily an application, the repo contains data/research-like elements in the profiling module (workload definitions, EC2 calibration scripts, JFR analysis) and the test262 conformance suite for the JS engine. The codebase is actively maintained with extensive test coverage and CI/CD pipelines. Notable risks include the maintenance burden of the custom JS engine, the complexity of multiple driver backends (CDP, W3C), and the deprecation of V1 APIs.
Mockoon is a multi-platform API mocking tool that runs mock servers locally or remotely. It is built as a monorepo with six npm packages: @mockoon/commons (shared models, migrations, OpenAPI converter), @mockoon/commons-server (core Express-based mock server engine with templating and response rules), @mockoon/app (Electron desktop application with an Angular renderer), @mockoon/cli (oclif-based command-line interface), @mockoon/cloud (cloud sync library), and the deprecated @mockoon/serverless wrapper. The architecture cleanly separates the core server logic from the delivery mechanisms. The MockoonServer class provides an HTTP/HTTPS server with a sophisticated response rule engine, a Handlebars templating system with over 100 custom helpers (including deep Faker.js integration), CRUD operations on data buckets, WebSocket support, proxy mode, and a full admin API. The desktop app uses a Redux-like state management pattern with RxJS, ensuring predictable and testable UI state transitions. The codebase demonstrates high craftsmanship in several areas. The ResponseRulesInterpreter is a self-contained DSL for matching HTTP requests to mock responses. The TemplateParser provides an extensible helper registration system. The data migration system in commons is a textbook example of handling schema evolution for JSON-based data models. The project is actively maintained with a robust CI/CD pipeline, though it carries some technical debt such as a deprecated serverless package and disabled strict TypeScript mode in the desktop app.
Microcks is a cloud-native API mocking and testing platform that ingests API specifications (OpenAPI, AsyncAPI, gRPC, GraphQL, Postman, SoapUI, HAR, and protobuf) and dynamically generates live mock endpoints and contract conformance tests. It supports REST, SOAP, GraphQL, gRPC, and asynchronous protocols (Kafka, RabbitMQ, MQTT, NATS, WebSocket, Amazon SQS/SNS, Google PubSub). The architecture consists of a main Spring Boot web application with an Angular frontend, a separate Quarkus-based async minion for event-driven mocking and testing, and optional dependencies on MongoDB, Keycloak, Kafka, and external message brokers. The system provides a rich set of features: dynamic response dispatching based on request parameters, scriptable mocks (Groovy/JavaScript), a template engine for dynamic content, SLA management, webhook notifications, AI-assisted sample generation via OpenAI, and OpenTelemetry-based observability. It is a well-engineered, modular project with extensive test coverage and a clean separation of concerns.
Bruno is a comprehensive API client and testing tool built with Electron, React, and Redux. It provides a full-featured interface for creating, sending, and analyzing HTTP/WebSocket/gRPC/GraphQL requests, similar to Postman but with an open-source core. The application features a modular architecture with separate packages for the GUI (bruno-app), Electron main process (bruno-electron), CLI (bruno-cli), request handling (bruno-requests), file storage (bruno-filestore), and shared utilities (bruno-common). Key capabilities include environment and variable management with secure secret handling, pre-request and test scripting using a custom BruJS runtime, collection organization and workspaces, import/export from formats like Postman, OpenAPI, and Insomnia, mock server functionality, and code generation from requests. The UI uses styled-components for theming with light/dark/system themes, and incorporates advanced features like AI-assisted request building and OpenAPI synchronization. The codebase demonstrates strong engineering practices with extensive unit and end-to-end testing, TypeScript throughout, and a clean separation of concerns between the main and renderer processes via IPC. Notable reusable components include a secure variable interpolation system, cross-platform detection utilities, persistent state hooks, and a worker-offloaded file format parser.
This repository is a PHP implementation of the Pact contract testing framework, enabling consumer-driven contract testing for APIs and microservices. It allows developers to define expected interactions in consumer tests (generating Pact files) and verify provider compliance against those contracts. The library supports multiple transport protocols (HTTP/REST, gRPC, message queues) and data formats (JSON, XML, CSV, Protobuf, etc.) through a plugin architecture. It uses FFI to interface with a Rust-based Pact core and includes a mock server for simulating providers during testing. The codebase features a well-structured domain model, extensive matcher/generator system, and comprehensive compatibility suite validating adherence to Pact specifications v1-v4.
Mentoss is a utility library for mocking JavaScript fetch() requests and responses in testing environments. It provides three primary classes: MockServer for defining request/response routes, FetchMocker for creating mocked fetch functions that work with one or more MockServers, and MockAgent for undici Dispatcher support in Node.js environments. The library handles complex HTTP features including CORS, credentials, redirects, and various request matching scenarios (URL parameters, headers, body content). The architecture is modular and well-separated, with distinct responsibilities for route matching (request-matcher.js), CORS handling (cors.js), cookie management (cookie-credentials.js), and request/response processing. Each MockServer instance maintains its own route registry and tracks which routes have been called, enabling precise test assertions. The FetchMocker coordinates multiple servers and handles cross-origin requests with proper CORS preflighting and credential attachment. Mentoss is designed for use in test suites where developers need to simulate HTTP interactions without making actual network calls. It supports both browser-like fetch() behavior (with baseUrl and credentials options) and Node.js undici/fetch() usage (via MockAgent). The library includes comprehensive testing helpers to verify which routes were called, assert all routes were exercised, and diagnose mismatched requests through detailed tracing.
Stoplight Prism is an open-source HTTP mock server and validation proxy driven by OpenAPI specifications (v2, v3, v3.1) and Postman Collections. It provides two primary CLI commands: `prism mock` to simulate an API from a schema definition, and `prism proxy` to validate requests and responses against a spec while forwarding traffic to a real upstream. The architecture is a monorepo with four packages (`core`, `http`, `http-server`, `cli`) that implement a functional pipeline: route matching, input validation (body, headers, query/path parameters, security), content negotiation, and response generation (static examples or dynamic faker-generated data). It also supports callback mocking, CORS handling, and RFC 7807 problem detail errors. The codebase is written in TypeScript with heavy use of fp-ts for composable error handling and dependency injection via reader monads. While the project is mature and well-tested (unit, integration, and a text-based harness test suite), its tight coupling to Stoplight internal packages and the steep learning curve of fp-ts reduce its overall reusability for external projects. It is not a data research repository.
JSON Server v1 (beta) is a CLI tool and library that spins up a fully functional REST API from a JSON or JSON5 file. It is built on top of lowdb for data persistence and @tinyhttp/app for HTTP handling. The architecture is a clean three-layer design: a CLI entry point (bin.ts) that wires file watching and server startup, an Express-like app layer (app.ts) that defines routes and parses query parameters, and a service layer (service.ts) that encapsulates all data access, filtering, pagination, and relationship embedding. The system supports advanced query capabilities including field operators (gt, lt, in, contains, etc.), JSON-based _where queries, sorting, pagination with navigation metadata, and resource embedding via _embed. It also handles referential integrity on deletes by nullifying foreign keys or cascading dependent deletions. The codebase demonstrates solid TypeScript craftsmanship with strict mode enabled, modern ESM modules, and a clear separation of concerns. Notable engineering patterns include the NormalizedAdapter wrapper that enforces string IDs and strips $schema on read while re-injecting it on write, and the Observer adapter that intercepts lowdb read/write lifecycle events to enable file-watch reloading without feedback loops. The query parsing layer cleanly separates URLSearchParams-based operator syntax from raw JSON _where objects, with proper type coercion for booleans, null, and numbers. The project is in active beta (v1.0.0-beta.15) with recent commits, CI via GitHub Actions, and a pre-commit hook running tests. It targets Node.js >=22.12 and leverages experimental TypeScript stripping for development. Dependencies are current and well-chosen (lowdb v7, @tinyhttp v3, eta v4). The test suite uses Node's built-in test runner and covers the service layer, query parsing, pagination, and full HTTP integration tests.
Moco is a Java library and standalone server for creating mock HTTP servers, primarily used for integration testing. It supports HTTP/HTTPS, REST, WebSocket, SSE, CORS, proxy with failover/playback, recording/replaying, and template-based responses. Architecture is modular: moco-core provides interfaces and implementations (Netty-based server, request matchers, response handlers), moco-runner adds a CLI for JSON-based configuration and standalone execution, and moco-junit/moco-junit5 provide JUnit integration. The system is configured either via a fluent Java API (central `Moco` static factory) or JSON configuration files, making it easy to stub endpoints in tests or as a standalone mock service. It uses Netty for high-performance HTTP serving, Jackson for JSON processing, Freemarker for templates, and Guava for utilities. The codebase is well-structured with clear separation of concerns, extensive tests, and support for modern protocols like HTTP/2 and WebSocket.