Backtesting proves whether a betting strategy would have made money in the past before you risk real money on it, and it is the single most important step between having an idea and placing a bet.

You do not need to write code to backtest: a spreadsheet, historical odds data, and a clear set of rules are enough to test most strategies honestly.

The key rules are to define your strategy before you look at results, use out-of-sample data to confirm findings, and account for the bookmaker's margin, because a strategy that ignores the vig will look profitable when it is not.

Watch out for the classic traps: cherry-picking winning periods, tweaking rules until past results look perfect, and testing on too few bets to mean anything.