Pourquoi les résultats des tests analogiques et réels sont-ils différents?

def CancelPendingOrders():
    orders = _C(exchange.GetOrders)
    Log(len(orders))
    for order in orders:
          exchange.CancelOrder(order.Id,order)


def onTick():
    depth = _C(exchange.GetDepth)
    askprice = depth.Asks[0].Price-0.01
    bidprice = depth.Bids[0].Price+0.01
    if bidprice<askprice:
        bidprice = askprice+0.01
    CancelPendingOrders()
    
    exchange.Sell(askprice,30)
    exchange.Buy(bidprice,30)


def main():
    while (true):
        onTick()
        Sleep(2000)