mockserver-monorepo

MockServer is an HTTP(S) mock server and proxy for testing that does three things: mock the APIs your application depends on, proxy real traffic to record, inspect and modify it (including pausing at interactive proxy breakpoints, like a debugger for network calls), and inject chaos such as latency, dropped connections and errors to test how your application copes. One port handles HTTP/1.1, HTTPS, HTTP/2, gRPC and gRPC-Web, WebSockets and raw TCP, detected automatically from the first bytes of each connection.

Features include matching requests on method, path, query, headers, cookies and body (JSON, XML, JSONPath, XPath, regex or OpenAPI), response templating (Velocity, Mustache, JavaScript), generating expectations from an OpenAPI specification, verifying which requests arrived and in what order, mocking of Kafka and MQTT message brokers, and a live dashboard. For AI work it can mock chat-completion APIs for OpenAI, Anthropic, Gemini, Bedrock, Azure OpenAI and Ollama including streaming, and includes a built-in MCP server for AI coding assistants. Clients exist for Java, JavaScript, Python and Ruby with JUnit and Spring support, and it runs from Docker, Helm, JAR or WAR. It is Apache-2.0 licensed.