When trading with a demo account you need to ensure live price feeds for accurate trading simulation. (londonforexopen.com)
To facilitate your practice below are three trading simulation sites that are easy to use. (tradingonlinemarkets.com)
Basically, such trading simulation shows a more accurate picture of the past performance and especially if the EA is sensitive to different price quotes and trading costs like spread and slippage. (mt4backtest.com)