Introduction to MCP Jest
MCP Jest is a comprehensive testing framework designed specifically for Model Context Protocol (MCP) servers. It brings the familiar Jest testing experience to the world of AI-powered tools and integrations.
What is MCP?
The Model Context Protocol (MCP) is an open standard that enables seamless integration between AI models and external tools. It allows AI assistants to interact with databases, APIs, and other services in a structured, type-safe manner.
Why Test MCP Servers?
Testing MCP servers is crucial because:
- Reliability: AI applications depend on your server's responses. Bugs can cascade into incorrect AI behavior.
- Type Safety: MCP uses strongly-typed schemas. Tests ensure your implementations match the declared types.
- Edge Cases: AI models may send unexpected inputs. Testing helps handle these gracefully.
- Regression Prevention: As you add features, tests ensure existing functionality remains intact.
Core Features
🧪 Comprehensive Testing
Test tools, resources, prompts, and server capabilities with a unified API.
📸 Snapshot Testing
Capture and validate server responses to detect unintended changes.
🚀 Fast Execution
Parallel test runs and smart caching for lightning-fast feedback.
🔧 CI/CD Ready
Integrate seamlessly with GitHub Actions, GitLab CI, and more.
How It Works
MCP Jest works by spinning up your MCP server, establishing a connection, and running a series of tests against it. Each test can:
- Send requests to your server (tool calls, resource reads, etc.)
- Validate the responses against expected schemas
- Check for specific values or patterns
- Compare responses with saved snapshots
The framework handles all the complexity of server lifecycle management, connection handling, and result reporting, letting you focus on writing meaningful tests.