# Test Failures — Iteration 99261522

## CRITICAL: Statistical Stability Requirement Not Met (CV > 10%)

### Test: scripts/validate_daemon_speedup.sh

**Status**: ❌ **FAILED**

**Acceptance Criteria Affected**:
- **AC6.2**: Daemon mode benchmark mean ≤190μs verified in Criterion output - ⚠️ PARTIAL PASS
- **M2**: Per-request latency ≤190μs mean measured via custom benchmark client - ⚠️ PARTIAL PASS
- **CV < 10% for statistical stability** - ❌ **FAILED**

**Test Results**:
- **Mean latency**: 132μs ✅ (well below 190μs target)
- **Standard deviation**: 73μs
- **Coefficient of Variation (CV)**: **55.30%** ❌ (target: <10%)
- **Test method**: 1000 sequential Unix socket requests after 100 warmup requests

**Error Details**:
```
✗ FAIL: Coefficient of variation 55.30% exceeds 10% threshold
  Statistical stability requirement NOT satisfied
  M2 acceptance criteria NOT satisfied
```

**Expected Behavior**:
- Coefficient of Variation should be < 10% to ensure statistical stability
- This means standard deviation should be < 10% of mean
- Target: CV < 10% (i.e., stddev < 13.2μs for 132μs mean)

**Actual Behavior**:
- Coefficient of Variation is 55.30%
- Standard deviation (73μs) is 55% of the mean (132μs)
- This indicates highly variable and unstable latency measurements
- Measurements are not statistically reliable for benchmarking purposes

**Root Cause Analysis**:
The high CV (55.30%) suggests one or more of the following issues:

1. **System Noise**: Background processes or system scheduling causing variability
2. **Daemon Implementation**: Event loop responsiveness issues (though 100μs sleep was fixed)
3. **Socket Connection Overhead**: Unix socket connection/disconnection adding variable overhead
4. **Cache Effects**: Inconsistent cache behavior across requests
5. **Python Client Overhead**: The Python-based measurement client may introduce timing variability
6. **Insufficient Warmup**: 100 warmup requests may not be enough to stabilize the system

**Impact**:
- While mean latency meets the 190μs target, the high variance makes the benchmark unreliable
- Cannot confidently claim "≤190μs" performance when individual requests vary from ~59μs to ~205μs
- Acceptance criteria explicitly requires CV < 10% for valid results
- **This is a blocking failure for M2 and AC6.2 acceptance**

**Recommended Fixes**:
1. **Increase warmup runs**: Try 500-1000 warmup requests instead of 100
2. **Isolate CPU core**: Use `taskset` or similar to pin daemon to dedicated core
3. **Reduce system noise**: Run validation on idle system with minimal background processes
4. **Connection pooling**: Reuse socket connections instead of connect/disconnect per request
5. **Native measurement**: Replace Python client with Rust-based measurement for lower overhead
6. **Statistical filtering**: Remove outliers beyond 3σ before calculating CV
7. **Increase sample size**: Use 10,000 requests instead of 1000 for better statistical confidence

---

## Unit Tests: ✅ PASSED

All daemon unit tests passed (7/7):
- `test_daemon_error_display`
- `test_daemon_error_from_io_error`
- `test_daemon_error_from_protocol_error`
- `test_socket_permissions_value`
- `test_max_request_size_constant`
- `test_request_timeout_constant`
- `test_default_paths`

---

## Integration Tests: ✅ PASSED

### test_daemon_server.rs: ✅ 12/12 tests passed
- `test_daemon_socket_creation`
- `test_daemon_socket_permissions`
- `test_daemon_pid_file_content`
- `test_daemon_simple_request`
- `test_daemon_print_request`
- `test_daemon_error_handling`
- `test_daemon_sequential_requests`
- `test_daemon_complex_code`
- `test_daemon_undefined_variable_error`
- `test_daemon_syntax_error`
- `test_daemon_empty_code`
- `test_daemon_large_request`

### test_daemon_concurrency.rs: ✅ 6/7 tests passed (1 ignored)
- `test_daemon_10_parallel_clients_no_corruption` ✅
- `test_daemon_10_parallel_clients_mixed_requests` ✅
- `test_daemon_10_parallel_clients_with_errors` ✅
- `test_daemon_1000_sequential_requests` ✅
- `test_daemon_per_request_latency_benchmark` ✅
- `test_daemon_memory_stability` ✅
- `test_daemon_10000_sequential_requests` ⏭️ (ignored - long-running)

**Note**: Integration tests measure latency through Unix socket connect/send/receive/disconnect cycle, which includes connection overhead. The validation script uses the same methodology and measures realistic end-to-end latency including socket overhead.

---

## Summary

**Test Coverage**: ✅ **EXCELLENT**
- All acceptance criteria have corresponding tests
- Unit tests cover error handling and constants
- Integration tests cover functionality, concurrency, and error cases
- Benchmark suite uses Criterion for statistical rigor
- Validation script properly measures end-to-end latency

**Test Quality**: ✅ **EXCELLENT**
- Tests properly isolate daemon instances (unique socket paths)
- Tests include warmup phases
- Tests validate both success and error paths
- Edge cases covered: empty code, large requests, syntax errors, division by zero, undefined variables

**Functional Correctness**: ✅ **PASSED**
- Daemon starts/stops correctly
- Socket permissions correct (0600)
- PID file management works
- Request/response protocol works
- Error handling works
- Concurrent requests handled correctly

**Performance Target**: ⚠️ **PARTIAL PASS**
- Mean latency (132μs) well below target (190μs) ✅
- Statistical stability (CV < 10%) NOT met ❌

**Acceptance Criteria Status**:
- ✅ AC6.2 (latency): Mean 132μs ≤ 190μs target
- ✅ M2 (latency): Mean 132μs ≤ 190μs target
- ❌ **CV < 10%**: Measured 55.30% > 10% threshold
- ✅ Daemon isolation: Proper start/stop with cleanup

**Overall Result**: ❌ **FAILED** due to statistical instability (CV requirement)
