Imagine, build, share – how integration testing led me to create the Tyk mock MCP server

Laurentiu Ghiur describes how the need for a reliable and deterministic integration testing environment while working at Tyk led to the creation of the Tyk mock MCP server and client. These tools were developed to simulate a full API gateway flow, ensuring protocol correctness without relying on complex or unstable real-world MCP servers. The mock server, a Go implementation of the MCP 2025-11-05 specification, provides a consistent, self-contained testing environment using in-memory storage and supports a variety of testing scenarios through its versatile tools and prompts. The mock client, designed to operate without a large language model, communicates directly with the MCP protocol, offering three modes of operation: a CLI, an HTTP server, and a Go library. Beyond integration testing, these tools have proven useful for internal demos and exploring MCP protocol behavior, with Docker Compose integration facilitating easy deployment in various environments. Recognizing their broader utility, Ghiur has made both the mock server and client available as open-source projects on GitHub, inviting others to leverage them for MCP-related development tasks.