How accurate is back test? (For Past Result)

Hi,

Can anyone tell me how accurate is back test for past result (Not future result). I know bast performance do not guarantee future result.

So, here i am asking about a past result.

I made a back test for EA (Oct 2020) and the result is in negative but the developer of EA said me back test provide false result and for him October 2020 was profitable with same EA which given a negative result with back test.

Can anyone clear my doubt?

Its surprisingly common that backtesters use a system that has no rules for trade exit - no SL and no TP. So when the system finds a rising chart, it just keeps buying and buying, whereas when this chart turns negative, it stops buying but never closes the losers.

Watch out for these tricks.

HI, the back test result is influenced, among others, by data quality, market settings (spread size, fees) and testing period. Regards Greg

It can be very accurate but you have to see what type of market it was then. It could of been a consolidating market and now its a trending one.