When the equity curve is too smooth, suspect the test

[Amanhasnoname]

A beautiful, straight equity curve in a backtest is a warning sign, not a reward. Real trading produces drawdowns, flat stretches, and irregularity. A curve with almost no pullbacks usually arises from an error or an unrealistic assumption.

Common causes include look-ahead bias, ignoring spreads, assuming fills at ideal prices, using the wrong side of the quote, and tuning parameters to the sample. Martingale and grid systems also produce smooth curves for long periods before collapsing.

Check the ratio of average profit to the standard deviation of trade results, and compare it to what is plausible for the market. Examine the largest trades and ask whether such fills would have been possible.

Look at the worst day, the longest drawdown, and the number of consecutive losers. If they are tiny, scrutinize the logic.

A test of robustness, such as adding slippage, doubling spreads, or delaying entries by a second, quickly separates fragile curves from solid ones.

Healthy systems show noise even in good conditions.

Which stress tests does the system face before it is trusted?