I am trying to develop a strategy for trading, and I want to get some opinions on what some of you think about what constitutes "sufficient" backtesting. I will supply my own ideas and perhaps that will help elicit some feedback. How many years back to test? I think roughly 5-7 years is good, since that is "recent history" in terms of the equity market trading patterns, given new technologies etc. Any difference of opinion on that? In my opinion the best way to gauge the success of a system is to give it an "imaginary" money account, let it trade that account, and the more money it makes, the better it is. Other methods may include percentage of winning trades, or average gain per trade (win or lose). Any opinions from those who have developed successful strategies? As far as accounting for all the variables, I figure give my trades 0.07 per share slippage, always try to use intra-day data if the trades are short, and don't let my simulation make trades so large that they disturb the market price if actually traded. And account for commisions of course. Anything missing? Any disagreement on anything here? If using adaptive optimization, you should always do "out-of-sample" testing as the measure of success. Anyone have more to say about the sufficiency of backtesting? What have you done to verify the soundness of a successful technique before implementing it?