backtesting-frameworks

# Backtesting Frameworks Build robust, production-grade backtesting systems that avoid common pitfalls and produce reliable strategy performance estimates. ## When to Use This Skill - Developing trading strategy backtests - Building backtesting infrastructure - Validating strategy performance - Avoiding common backtesting biases - Implementing walk-forward analysis - Comparing strategy alternatives ## Core Concepts ### 1. Backtesting Biases | Bias | Description | Mitigation | | ---------------- | ------------------------- | ----------------------- | | **Look-ahead** | Using future information | Point-in-time data | | **Survivorship** | Only testing on survivors | Use delisted securities | | **Overfitting** | Curve-fitting to history | Out-of-sample testing | | **Selection** | Cherry-picking strategies | Pre-registration | | **Transaction** | Ignoring trading costs | Realistic cost models | ### 2. Proper Backtest Structure ``` Historical Data │ ▼ ┌─────────────────────────────────────────┐ │ Training Set │ │ (Strategy Development & Optimization) │ └─────────────────────────────────────────┘ │ ▼ ┌─────────────────────────────────────────┐ │ Validation Set │ │ (Parameter Selection, No Peeking) │ └─────────────────────────────────────────┘ │ ▼ ┌─────────────────────────────────────────┐ │ Test Set │ │ (Final Performance Evaluation) │ └─────────────────────────────────────────┘ ``` ### 3. Walk-Forward Analysis ``` Window 1: [Train──────][Test] Window 2: [Train──────][Test] Window 3: [Train──────][Test] Window 4: [Train──────][Test] ─────▶ Time ``` ## Detailed worked examples and patterns Detailed sections (starting with `## Implementation Patterns`) live in `references/details.md`. Read that file when the navigation summary above is insufficient. ## Best Practices ### Do's - **Use point-in-time data** - Avoid look-ahead bias - **Include transaction costs** - Realistic estimates - **Test out-of-sample** - Always reserve data - **Use walk-forward** - Not just train/test - **Monte Carlo analysis** - Understand uncertainty ### Don'ts - **Don't overfit** - Limit parameters - **Don't ignore survivorship** - Include delisted - **Don't use adjusted data carelessly** - Understand adjustments - **Don't optimize on full history** - Reserve test set - **Don't ignore capacity** - Market impact matters