Backtesting fundamentals

Time and availability

A test must use only information available at each decision timestamp. A daily high is not known at the start of the day. Indicators must be computed without future closes. Preserve timezone, completed-bar rules and missing-data flags. An ordered candle array alone does not establish executable prices.

Model execution honestly

A bar does not reveal the intrabar order in which its high and low occurred. If both stop and target lie inside its range, record ambiguity or apply a documented conservative assumption. Include spreads, fees, gaps and slippage assumptions. Never call a filled synthetic candle a historical market execution.

Know this platform boundary

LEGION provides practice charts, indicators, history and realized statistics; it does not provide an automated historical strategy backtester. Exported CSV is recorded DEMO activity, not a validated strategy test. Offline modeled charts are unsuitable for proving profitability. Obtain authorized, suitable historical data before external research.

Practice exercise

Describe one look-ahead error and one ambiguous stop/target bar. Explain why importing a CSV into a spreadsheet does not itself validate a strategy.

Open trading terminal (requires a customer account). Compare illustrative indicators.