Trading with forex expert advisors is a tricky thing so you need to be able to be able to forecast corectly which will work in the future.The forex trading robots can be many types. There are trend following systems, there are range systems and there are mixed one. The backtesting can give you some information about the maximum drawdown in history , but it deffinitely cannot tell you what will happen in the future. However without backtest you don't know if a system is good or bad. The other option that people can use is the grid trade With that option you can always win and stay market neutral. Of course there is always risk . The biggest risk is the big trend. You can be always sure that the big forex trend will come and that it can be bigger that any historical for that period . So when setting the parameters of the system you must make sure you expect even 50% higher thant the highest trend.