test(mcp-server): add MCP protocol E2E tests (Phase 1)

[JeremyDev87]

Parent

E2E test infrastructure initiative.

Problem

The MCP server (apps/mcp-server/) is the core product but has zero E2E tests. Unit tests cover 84 files at 80% coverage, but no test verifies the actual MCP protocol handshake, tool invocation, or transport layer (stdio/SSE) end-to-end.

A broken stdio transport or malformed JSON-RPC response would only be caught in production.

Scope

New directory: apps/mcp-server/tests/e2e/

stdio transport tests (~8 tests)

• MCP handshake: initialize → initialized response with capabilities
• Tool listing: tools/list returns all registered tools
• Tool invocation: search_rules with query → valid result
• Tool invocation: get_agent_details with agent name → valid result
• Tool invocation: activate with prompt → rules + specialists
• Resource listing: resources/list returns rules:// resources
• Resource read: resources/read with valid URI → content
• Error handling: invalid JSON-RPC request → proper error response

SSE transport tests (~5 tests)

• SSE endpoint accepts connection and sends events
• Tool call via HTTP POST → SSE event with result
• Bearer token auth: valid token → 200, missing token → 401
• Multiple concurrent SSE connections
• Graceful disconnection

Error edge cases (~3 tests)

• Non-existent tool name → JSON-RPC error
• Malformed tool arguments → meaningful error
• Large payload handling (oversized query)

Technical approach

• Framework: Vitest (matches existing setup)
• stdio: child_process.spawn the compiled server, write JSON-RPC to stdin, read stdout
• SSE: Start NestJS TestingModule with HTTP listener, connect via fetch + EventSource
• Config: Separate vitest.config.e2e.ts with extended timeout (30s)
• CI: Add e2e-mcp job to .github/workflows/dev.yml (runs after build)

Test commands

yarn workspace codingbuddy test:e2e        # Run MCP E2E tests
yarn workspace codingbuddy test:e2e:stdio   # stdio transport only
yarn workspace codingbuddy test:e2e:sse     # SSE transport only

Acceptance criteria

• apps/mcp-server/tests/e2e/ directory with ≥15 tests
• stdio transport: handshake + tool call + resource read + error
• SSE transport: connection + tool call + auth + disconnect
• vitest.config.e2e.ts with 30s timeout
• test:e2e script in package.json
• CI job passes on PR
• No mocking of MCP transport — real stdin/stdout or real HTTP

Out of scope

• Performance/load testing
• Prompt content validation (covered by unit tests)
• Plugin ↔ MCP integration (Phase 3)