WebSocket Integration Testing - NO MOCKS

Overview

Test WebSocket servers with functional testing: real connections, real filesystem, real protocol validation.

Core principle: NO MOCKS. Test actual behavior. Verify filesystem changes.

Announce at start: "I'm using the websocket-integration-testing skill for functional WebSocket testing."

REQUIRED BACKGROUND: @testing-anti-patterns (explains NO MOCKS principle)

When to Use

• Testing WebSocket servers (Gate 3A)
• Validating message protocol compliance
• Testing tool execution through WebSocket
• Verifying session management
• Integration testing (Gates 6A-E)

Quick Reference

Core Workflow

1. Start Backend

mcp__serena__execute_shell_command({
  command: "cd backend && npm start",
  cwd: "/Users/nick/Desktop/claude-mobile-expo"
});

2. Connect with wscat

mcp__serena__execute_shell_command({
  command: "wscat -c 'ws://localhost:3001/ws'"
});

3. Send init_session

{"type":"init_session","projectPath":"/tmp/test-project"}

VERIFY: session_initialized with UUID received

4. Test Tool Execution

{"type":"message","message":"Create a test.txt file with 'Test content'"}

VERIFY:

• tool_execution message received ✅
• tool_result shows success ✅
• File ACTUALLY created (check filesystem) ✅

// CRITICAL: Verify real file exists
mcp__serena__read_file({
  relative_path: "../../../tmp/test-project/test.txt"
});
// Must return: "Test content"

5. Test All Tools

For each tool, verify ACTUAL filesystem/git changes:

• write_file → File exists on disk ✅
• read_file → Content returned correctly ✅
• list_files → Directory listing matches actual files ✅
• execute_command → Command actually ran ✅
• git_status → Real git status ✅
• git_commit → Commit in git log ✅

6. Use Automation Script

mcp__serena__execute_shell_command({
  command: "./scripts/test-websocket.sh ws://localhost:3001/ws /tmp/test-project"
});

Exit code 0 = all pass

NO MOCKS Principle

❌ WRONG: Unit tests with mocks

// DON'T do this:
jest.mock('ws');
const mockWs = {send: jest.fn(), on: jest.fn()};

jest.mock('fs');
fs.writeFileSync = jest.fn();

Why wrong: Testing mock behavior, not real system

✅ CORRECT: Functional testing

// Real WebSocket connection
import WebSocket from 'ws';
const ws = new WebSocket('ws://localhost:3001/ws');

// Real file verification
import fs from 'fs';
const content = fs.readFileSync('/tmp/test-project/test.txt', 'utf8');
assert(content === 'Test content');

Why correct: Testing actual system behavior

Common Mistakes

Red Flags

• "Mocks are sufficient" → WRONG. NO MOCKS.
• "Skip protocol tests" → WRONG. Test all message types.
• "Unit tests first" → WRONG. Functional tests only.

Integration

• Use FOR: Validation Gate 3A
• Use WITH: @claude-mobile-validation-gate
• Principle FROM: @testing-anti-patterns (NO MOCKS)