Since 2008 the most of the dealing centers began to work with the "floating" spreads. During the night the spreads are often wider. The wide spreads are appear during the news.
The spread increasing can be sufficient, so in such cases some trading systems cannot be profitable. The stop level can be increased several times, it may cause the incorrect work of the Expert Advisors with fixed Stop Loss and Take Profit values.
The Strategy Tester of MetaTrader 4 client terminal uses the last known values of spread, stop level and freeze level, the result is dependent on these values. The Strategy Tester of MetaTrader 5 client terminal uses the historical spread values, the structure of historical data prices has the corresponding field.
The spread_on_chart indicator shows the following values on the chart:
It updates every tick.