Adds testBacktestEngine.ts — the minimum viable test set called out in
docs/backtest/ENGINE_READINESS.md §3.1. Codifies behaviors verified
during the readiness audit so they don't silently regress.
Coverage (10 assertions, all passing):
Unit (testable building blocks):
- aggregateCandles 15m→1h: OHLC preserved, volume summed
- aggregateCandles 15m→4h: OHLC preserved, volume summed
- computeSummary: hand-computed PnL/winRate/drawdown match
- computeSummary: empty inputs → all zeros (no NaN/Infinity)
- computeSharpe: single-point timeline → 0 (no divide-by-zero)
- withLogLevel: level restored after success AND after throw
Integration (full runBacktest):
- Determinism: same input → byte-identical JSON output
- Flat-price tape → 0 trades, 0 PnL, 0 drawdown
- Result shape contract: all documented top-level keys present
- Empty candle dataset throws explicitly (no silent 0-trade result)
Conforms to the existing testXxx.ts convention used by the other
check:backtest-* scripts. Wired into package.json:
- "check:backtest-engine": "node --import tsx testBacktestEngine.ts"
- chained into the top-level "test" script
Generated with [Devin](https://cli.devin.ai/docs)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
