Backtesting Fundamentals
Backtesting validates trading strategies against historical market data before risking real capital. Quality backtesting requires tick-level data (not just OHLC candles), realistic spread and commission modeling, slippage simulation, and proper handling of gaps, dividends, and corporate actions. The goal is to simulate live trading conditions as accurately as possible.

Tools and Platforms
MetaTrader's Strategy Tester provides basic backtesting for EA developers. Python with Backtrader or Zipline offers flexibility for custom strategies. QuantConnect and TradingView provide cloud-based backtesting with extensive data libraries. For institutional strategies, commercial platforms like MultiCharts and NinjaTrader offer tick-level precision and multi-asset support.
Avoiding Common Traps
Overfitting is the most dangerous pitfall: optimizing parameters to fit historical data perfectly while creating a strategy that fails in live markets. Combat overfitting by using out-of-sample testing periods, walk-forward optimization, and Monte Carlo simulations. Validate results across different market regimes (trending, ranging, volatile) to ensure robustness.