Backtesting Invalidation

Backtesting invalidation happens when the results of a strategy's historical performance testing are proven to be unreliable in live trading. This occurs due to errors in the testing environment, such as ignoring transaction costs, slippage, or market impact.

It can also happen if the backtest suffers from look-ahead bias, where future information is inadvertently included in the past data. When a strategy performs perfectly in a backtest but fails in reality, it indicates that the backtest did not accurately reflect market conditions.

This is a common pitfall for new quantitative traders. Ensuring that backtesting is robust and realistic is the only way to validate a strategy before deploying capital.

It is a fundamental step in the development of any financial derivative strategy.