code: def test_iadd(mock_exchange_class, mock_order_spec_class):
      exchange = mock_exchange_class.return_value
      exchange.options = ExchangeOptions()
      exchange.id = "fake_exchange_id"
      exchange.name = "bitfinex"
      exchange.clock = mock.Mock()
      exchange.clock.step = 0
      exchange.quote_price = mock.Mock(return_value=Decimal(7000.00))
  
      wallets = [
          Wallet(exchange, 10000 * USD),
          Wallet(exchange, 0 * BTC),
      ]
      portfolio = Portfolio(USD, wallets)
  
      # Market order
      order = Order(
          step=0,
          exchange_pair=ExchangePair(exchange, USD / BTC),
          side=TradeSide.BUY,
          trade_type=TradeType.MARKET,
          quantity=5000.00 * USD,
          portfolio=portfolio,
          price=Decimal(7000.00),
      )
  
      order_spec = mock_order_spec_class.return_value
  
      assert len(order._specs) == 0
      order.add_order_spec(order_spec)
      assert len(order._specs) == 1
  
      assert order_spec in order._specs
  
imports: import re
  import unittest.mock
  from decimal import Decimal
  from tensortrade.oms.instruments import *
  from tensortrade.oms.orders import Order, OrderStatus, OrderSpec, TradeSide, TradeType
  from tensortrade.oms.orders.criteria import Stop
  from tensortrade.oms.exchanges import ExchangeOptions
  from tensortrade.oms.wallets import Wallet, Portfolio
label_desc: Use image node_id 15 for calling a global function with example usage: test_iadd(mock_exchange_class, mock_order_spec_class) without return types