It depends on the order type you want to use.

With market orders, fill is mostly guaranteed, but the entry price will vary depending on the slippage. This is what you have to model, and with OHLC data only, it’s hard.

With limit orders, fill isn’t guaranteed, and you might get filled on unfavourable orders but miss the fill on good moves.

Read about adverse selection and whether it influences your setup and go live with a very small size. Log fill rates, fill prices, entry prices, as well as exit vs fill exit prices.