@debugmcp/mcp-debugger/docs/archive/refactoring/task-6-mock-adapter-completion-summary.md

Run-time step-through debugging for LLM agents.

# Task 6: Mock Adapter Completion Summary

## 🎯 Objectives Achieved

### 1. ✅ Mock Adapter as Production Component
- Implemented Mock adapter as a **real debugging adapter**, not a test mock
- Provides simulated debugging functionality for demos, training, and CI environments
- Follows the same patterns as the Python adapter

### 2. ✅ Complete DebugAdapter Interface Implementation
The Mock adapter now implements all required methods:
- `launch()` - Initializes mock session with stopOnEntry support
- `setBreakpoints()` - Stores and verifies breakpoints
- `continue()` - Simulates execution with deterministic breakpoint hits
- `next()`, `stepIn()`, `stepOut()` - All stepping operations functional
- `pause()` - Interrupts simulated execution
- `getStackTrace()` - Returns realistic mock call stacks
- `getScopes()` - Provides Local and Global scopes
- `getVariables()` - Returns typed variables matching test expectations

### 3. ✅ Realistic State Machine
- Tracks execution state: running, stopped, terminated
- Deterministic breakpoint behavior (always stops at next breakpoint)
- Proper event sequencing following DAP protocol
- Simulates execution timing with small delays

### 4. ✅ DAP Event Emission
Correctly emits all required events:
- `initialized` - When adapter is ready
- `stopped` - At breakpoints, steps, and entry
- `continued` - When resuming execution
- `terminated` - When "program" completes
- `exited` - After termination

## 🔧 Implementation Details

### Key Changes Made

1. **Mock Adapter Process (`src/adapters/mock/mock-adapter-process.ts`)**
   - Complete DAP server implementation
   - TCP and stdio communication support
   - Deterministic breakpoint handling (removed randomness)
   - Realistic variable data matching test expectations
   - Proper state tracking with `currentLine` and `isRunning`

2. **Mock Debug Adapter (`src/adapters/mock/mock-debug-adapter.ts`)**
   - Full DebugAdapter interface implementation
   - Spawn management for mock adapter process
   - Event forwarding from adapter process to proxy
   - Proper cleanup and termination handling

3. **Session Manager Updates**
   - Added language field to ProxyConfig
   - Fixed import issues with ProxyConfig
   - Proper handling of language-specific adapters

## 🧪 Testing Status

### Current Issues
While the Mock adapter is functionally complete, E2E tests are experiencing timing issues:
- Stack trace queries may occur before session state updates
- Need better synchronization between test expectations and adapter events

### Recommended Fixes
1. Increase wait times in tests for adapter state changes
2. Add explicit state checking before operations
3. Consider adding event-based waiting instead of fixed timeouts

## 📊 Production Readiness

The Mock adapter is ready for production use cases:
- ✅ Demos and presentations
- ✅ Training environments
- ✅ CI/CD pipelines without language runtimes
- ✅ Development and testing

## 🔍 Verification

To verify the Mock adapter implementation:

```bash
# Unit tests pass
npm test -- src/adapters/mock

# Can create mock debug sessions
node dist/index.js stdio
# Then use MCP tools to create session with language: "mock"

# E2E tests need timing adjustments
npm run test:e2e -- tests/e2e/full-debug-session.test.ts
```

## 📚 Usage Example

```javascript
// Create a mock debug session
const session = await createDebugSession({ language: 'mock' });

// Set breakpoints (will be verified)
await setBreakpoint(session.id, 'script.js', 10);

// Start debugging
await startDebugging(session.id, 'script.js', { stopOnEntry: true });

// Continue to breakpoint (deterministic)
await continueExecution(session.id);

// Inspect variables (returns x=10, y=20, result=30)
const vars = await getVariables(session.id, scopeRef);
```

## 🏁 Definition of Done Status

- [x] Complete DebugAdapter interface implementation
- [x] State machine tracks debugging flow correctly  
- [x] All DAP events emitted in proper sequence
- [x] Mock data realistic and consistent
- [ ] E2E tests pass with Mock adapter (timing issues remain)
- [x] Can demonstrate debugging without Python
- [x] Documented as production component

## 🔮 Future Enhancements

1. **Configurable Mock Behavior**
   - Allow custom variable values
   - Configurable execution timing
   - Script-specific behavior

2. **Enhanced Simulation**
   - Multi-threaded debugging simulation
   - Exception handling simulation
   - More complex call stacks

3. **Test Improvements**
   - Better event synchronization
   - Reduce timing dependencies
   - Add mock-specific test scenarios

## 📝 Conclusion

The Mock adapter has been successfully implemented as a production-ready component that provides lightweight debugging simulation. While E2E tests need timing adjustments, the adapter itself is fully functional and ready for use in demos, training, and environments without language runtimes.

The implementation follows the same patterns as the Python adapter, making it a good template for future language adapters. It demonstrates that the MCP debugger architecture can support multiple debugging backends with consistent behavior.