MCP Debugger

# examples/debugging/test-sse-js-debug-fix.js @source-hash: 8ab6dff3fc98d3eb @generated: 2026-02-10T00:41:45Z ## Purpose Integration test script for validating the fix to a timing bug in SSE (Server-Sent Events) JavaScript debugging where `stackTrace` was called before the child debugging session was fully active. ## Key Components ### Main Test Function - `runTest()` (L36-201) - **Primary Orchestrator**: Manages complete test lifecycle from server startup to cleanup - **Phases**: Server startup → Client connection → Debug session creation → Critical timing test → Cleanup - **Error Handling**: Comprehensive try-catch with guaranteed cleanup in finally block ### Port Availability Utility - `waitForPort()` (L15-34) - **Purpose**: Waits for SSE server to become available on specified port - **Parameters**: `port`, `maxAttempts` (default 30) - **Strategy**: Uses TCP connection attempts with 1-second intervals - **Returns**: Boolean success or throws error after max attempts ## Test Flow Architecture ### 1. Server Lifecycle (L44-66) - Spawns SSE server process using `child_process.spawn` (L45-53) - **Server Path**: `dist/index.js` with SSE mode and debug logging - **Port**: Fixed at 3100 for consistent testing - Captures stdout/stderr for debugging visibility ### 2. MCP Client Setup (L69-78) - Creates MCP client with SSEClientTransport - **Transport URL**: `http://localhost:${PORT}/sse` - **Client Identity**: 'test-sse-js-debug-fix' v1.0.0 ### 3. Critical Timing Test Sequence (L81-167) - **Debug Session Creation** (L82-97): Creates JavaScript debug session via MCP tool call - **Breakpoint Setup** (L100-111): Sets breakpoint at line 11 in target script - **Debug Start** (L114-123): Initiates debugging session - **CRITICAL TEST** (L125-167): Immediately calls `get_stack_trace` - this is where the original timing bug occurred - **Validation**: Checks for non-empty stackFrames array to confirm fix - **Additional Test** (L147-162): Also tests `get_local_variables` to ensure full session readiness ## Dependencies - **@modelcontextprotocol/sdk**: Client and SSEClientTransport for MCP communication - **child_process**: For spawning SSE server subprocess - **net**: For port availability checking - **path**: For file path resolution ## Key Constants - **PORT**: 3100 (L13) - Fixed test port - **Target Script**: `examples/javascript/simple_test.js` (L100) - **Breakpoint Line**: 11 (L108) ## Error Scenarios - Server startup failure or port unavailability - MCP client connection failure - Debug session creation failure - Empty stack trace (indicates timing bug still exists) - Tool call failures during debugging operations ## Cleanup Strategy - Guaranteed cleanup in finally block (L182-200) - Graceful client closure with error suppression - Server process termination (SIGTERM → SIGKILL fallback) - 1-second grace period for clean shutdown