Trouble shooting

Table of contents

• Vscode Windows: Debugging is not working
• Test Isolation: Socket.IO event listener accumulation

Vscode Windows: Debugging is not working

Date: 2025-03-08

⚠️ IMPORTANT: On Windows, please check out the repo on drive C. There is a bug in the VS Code Vitest extension (v1.14.4), which prevents test debugging from working: https://github.com/vitest-dev/vscode/issues/548 Please check from time to time if the issue has been fixed and remove this note once it is resolved.

Test Isolation: Socket.IO event listener accumulation

Date: 2025-01-28

Problem:

When running multiple tests that use Socket.IO connections, tests pass individually but fail when run together. This is caused by event listeners from previous tests remaining active on persistent socket instances.

Symptoms:

• Individual tests pass: ✅
• All tests together fail: ❌
• Error messages like "received 0 instead of expected number of nodes"
• Unexpected behavior when sockets receive messages from previous tests

Root Cause:

Socket.IO sockets persist across tests in the beforeAll setup. When SocketIoBridge instances are created in beforeEach, old event listeners accumulate on the underlying sockets, causing interference between tests.

Solution:

Clear all event listeners in beforeEach before creating new bridges:

beforeEach(async () => {
  // Remove all event listeners from previous test to prevent interference
  serverSockets.forEach((socket) => socket.removeAllListeners());
  clientSockets.forEach((socket) => socket.removeAllListeners());

  // Now proceed with test setup...
  server = new Server(route, serverIo, serverBs);
  await server.init();
  // ... rest of setup
});

Why This Works:

• removeAllListeners() clears accumulated event handlers
• Each test starts with clean sockets
• No interference from previous test's SocketIoBridge instances
• Maintains socket connections established in beforeAll

Alternative Approaches Considered:

1. ❌ tearDown() in afterEach: Caused hook timeouts
2. ❌ Creating new socket connections per test: Too slow, defeats purpose of beforeAll
3. ✅ Clear listeners while reusing connections: Fast and reliable