Validity of Backtests in MT3?

I have an EA that backtests very well in MT3. I haven't worked very much with MT3 in the past, so I'm just curious as to how accurate the backtester is? This particular EA trades on the daily charts, and it uses stops and t/p's for exits. Does MT3 look inside the bar?

Hello,

There are a few problems with MT3 backtesting:
1. the EA can place buy at bid and sell at ask - which is of course impossible in real life - so you need to check to make sure it is not the case
2. For all of the technical indicators, if it is using Price_close, Price_High, Price Low, with the "bar 0", the backtesting become absolutely useless. (it basically "predict" the future and won't give you the real time backtest result. (It also involve using Close[0], High[0], Low[0])

There may be some other problems that I can't really remember but those 2 are the "majors".
If those issues are not presented, the backtesting in MT3 are very consistent with the real time trade.