You can test your systems on real ticks and it will be same as you are trading (MT5) - read more on this article Testing trading strategies on real ticksand this is the explanation abouut -
Forum on trading, automated trading systems and testing trading strategies
PriceChannel Parabolic system
Sergey Golubev, 2017.02.15 06:02
You can read this article (TESTING TRADING STRATEGIES ON REAL TICKS).
-------------------Just an example - MT4 and very old builds of MT5: I optimized the EAs from this thread just to find good settings for the pair, I was backtesting them, and I traded on demo for some time just to be sure that EAs are profitable.With new builds of MT5: I will optimize the EAs from this thread to find the settings, and I will backtesting them with 'every tick based on real ticks' - and it will be same as trading by those EA on real account for many months or years!
MT4 & MT5 backtest
Sergey Golubev, 2017.02.17 20:53
If you are backtesting EA on MT5 using 'every tick based on real ticks' so it will be almost same with trading on MT5 platform with some particular broker (because it is based on actual historical data).
Example, read this thread: Why is it better MT5 than MT4?? Does it have fewer limitations ??? - this is the quote from the first post of the thread:
For more information about it - read this summary.
As i know - some coders/traders are converting their MT4 EAs to MT5 just to backtest them and/or to find the settings with optimization to get the backtesting results that are closest to reality.
You suppose variable spread is supported, but it's not display on the report and if you change the spread value in the tester you're getting different results : it is not supported.