Introduction to Using TDD to Build MCP

This presentation is an introduction to using test driven development (TDD) to develop a solution for model context protocol (MCP) primarily using Java.

The content is suitable for beginner to intermediate learners of either TDD or MCP.

The presentation was originally delivered to a group of my peers in an academic context.

Transcript

1. J U S T I N B I A R D / C O M P - 6 4 5 Q 1 W W A P R I L 1 , 2 0 2 5 TDD: TEST DRIVEN DEVELOPMENT
2. AGENDA • Context and requirements • Tools and libraries used • The process • Example solution • Conclusion
3. MODEL CONTEXT PROTOCOL (MCP)
4. MCP Tools[3] are to AI, as Remote Method Invocation (RMI) is to a Java program. CONTEXT
5. CONTEXT We are here… MCP Tools[3] are to AI, as Remote Method Invocation (RMI) is to a Java program.
6. REQUIREMENTS: MCP TOOLS ONLY • Requests and responses are delivered using JSON-RPC[1] formatted messages • For example, responses contain: • jsonrpc: the version (2.0) • result: optional • error: optional, unless there is an error • Id: a number or a string • MCP servers and clients collaborate to give Artificial Intelligence (AI) models access to retrieve specific context or to take specific actions (through tools) • For example, MCP tools define: • name: a short string name • arguments: the input schema • description: a text description of the tool JSON-RPC 2.0 MCP 2024-11-05:
7. DEVELOPER TOOLS + LIBRARIES • IntelliJ + Java • For development of the MCP tools and unit tests • Maven (+Make) • For automation of the build and MCP inspection pipeline • Bun • For debugging via MCP inspector • Claude Desktop • For execution of the MCP server • JDK 21 • JUnit Jupiter (5.12.0) • For unit test development • AssertJ (3.25.3) • For fluent-style assertions • Jackson Databind (2.18.3) • For mapping JSON to/from plain old Java objects (POJO) Developer Tools Libraries
8. THE PROCESS (THEORY) Test Driven Development[5]: requirement / test / fail / code / pass / refactor
9. THE PROCESS (PRACTICE) Test Driven Development[5]: requirement / test / fail / code / pass / refactor
10. EXAMPLE SOLUTION
11. TEST • Pick a requirement (“initialize server”[2]) and blocked out how we want the API to look • Identify placeholders for “Request” and “Response” which do not yet exist • Servers complying with this interface should return a protocol version, so we assert that value too
12. TEST • Pick a requirement (“initialize server”[2]) and blocked out how we want the API to look • Identify placeholders for “Request” and “Response” which do not yet exist • Servers complying with this interface should return a protocol version, so we assert that value too CODE • Create the Server interface • Define the placeholder method signatures • Define the Request and Response classes (as empty classes at this point) • Update import statements in ServerTest to address compiler warnings
13. TEST • Pick a requirement (“initialize server”[2]) and blocked out how we want the API to look • Identify placeholders for “Request” and “Response” which do not yet exist • Servers complying with this interface should return a protocol version, so we assert that value too CODE • Create the Server interface • Define the placeholder method signatures • Define the Request and Response classes (as empty classes at this point) • Update import statements in ServerTest to address compiler warnings REPEAT
14. COMPLETED TEST @Test void testServerInterface() { // given var server = new Server() { @Override public Response initialize(Request request) { return null; } @Override public Response listTools(Request request) { return null; } @Override public Response invokeTool(Request request) { return null; } @Override public Response handleRequest(Request request) { return null; } }; // when -> then assertThat(server.getProtocolVersion()).isNotBlank(); }
15. USING THE MCP TOOL IN CLAUDE[4] // claude_desktop_config.json { "mcpServers": { "tdd": { "command": "java", "args": [ "-jar", "path-to.jar" ] },… } }
16. USING THE MCP TOOL IN CLAUDE[4] // claude_desktop_config.json { "mcpServers": { "tdd": { "command": "java", "args": [ "-jar", "path-to.jar" ] },… } }
17. USING THE MCP TOOL IN CLAUDE[4] // claude_desktop_config.json { "mcpServers": { "tdd": { "command": "java", "args": [ "-jar", "path-to.jar" ] },… } }
18. USING THE MCP TOOL IN CLAUDE[4]
19. CONCLUSION
20. CONCLUSION What we saw: • MCP and MCP Tools as example requirements including the use of JSON-RPC
21. CONCLUSION What we saw: • MCP and MCP Tools as example requirements including the use of JSON-RPC • TDD, which is a useful process for iterative software development (my opinion) TDD + MCP
22. CONCLUSION What we saw: • MCP and MCP Tools as example requirements including the use of JSON-RPC • TDD, which is a useful process for iterative software development (my opinion) • An example MCP tool developed by TDD being used by Claude Sonnet 3.7 TDD + MCP
23. REFERENCES • [1] JSON-RPC 2.0 https://www.jsonrpc.org/specification • [2] MCP Lifecycle (Initialization): https://spec.modelcontextprotocol.io/specification/2024-11-05/basic/lifecycle/ • [3] MCP Tools: https://spec.modelcontextprotocol.io/specification/2024-11- 05/server/tools/ • [4] Claude for Desktop: https://support.anthropic.com/en/articles/10949351-getting- started-with-model-context-protocol-mcp-on-claude-for-desktop • [5] Larman, C. (2005). Applying UML and Patterns: An Introduction to Object-Oriented Analysis and Design and Iterative Development. (3rd ed. pp. 385-394). Wait, J.
24. THANK YOU