test: test orders usd amount

tests/orders/test_orders.py

@@ -0,0 +1,20 @@
+import pytest
+from typing import Union
+
+from auto_trading.orders import Short, Long
+
+
+@pytest.mark.parametrize(
+    "order, usd",
+    [
+        (Long("BTC", 1, 1), 1),
+        (Short("BTC", 1, 1), 1),
+        (Long("BTC", 1, 10), 10),
+        (Short("BTC", 1, 10), 10),
+        (Long("BTC", 10, 1), 10),
+        (Short("BTC", 10, 1), 10),
+    ],
+)
+def test_order_usd(order: Union[Long, Short], usd: float):
+    """Test the USD value of an order."""
+    assert order.amount_usd == usd