Does MT4 backtesting actually simulate market spread?

[Eli]

I want to know, If I set the spread in backtesting to 10, does that actually backtest the EA as if it was spread of 5 or 10 at the time?

EUR/USD on a live demo environment has 5-10 spread on FTMO, if I set spread to 5 or 10, will it actually give realistic results as if spread was 5 or 10 during that time?

Thanks,

[William Roeder]

Eli: I want to know, If I set the spread in backtesting to 10, does that actually backtest the EA as if it was spread of 5 or 10 at the time?

If you set it to ten (10), the spread will be a constant ten the entire backtest.

Variable spread is only in MT5.