test: add test for immediately triggering stop order

part of #12824

tests/exchange/test_exchange.py

@@ -1371,6 +1371,59 @@ def test_create_dry_run_order_limit_fill(
     order_closed = exchange.fetch_dry_run_order(order["id"])
 
 
+@pytest.mark.parametrize(
+    "side,price,error",
+    [
+        # order_book_l2_usd spread:
+        # best ask: 25.566
+        # best bid: 25.563
+        ("sell", 22.0, False),
+        ("sell", 25.55, False),
+        ("sell", 26.00, True),
+        ("buy", 30.0, False),
+        ("buy", 25.57, False),
+        ("buy", 22.57, True),
+    ],
+)
+@pytest.mark.parametrize("exchange_name", EXCHANGES)
+def test_create_dry_run_order_stoploss(
+    default_conf_usdt,
+    mocker,
+    exchange_name,
+    order_book_l2_usd,
+    side,
+    price,
+    error,
+):
+    default_conf_usdt["dry_run"] = True
+    exchange = get_patched_exchange(mocker, default_conf_usdt, exchange=exchange_name)
+    if not exchange.get_option("stoploss_on_exchange"):
+        pytest.skip(f"{exchange_name} does not support on exchange stoploss orders")
+
+    mocker.patch.multiple(
+        EXMS,
+        exchange_has=MagicMock(return_value=True),
+        fetch_l2_order_book=order_book_l2_usd,
+    )
+    params = {
+        "pair": "LTC/USDT",
+        "amount": 1,
+        "stop_price": price,
+        "order_types": {"stoploss": "limit"},
+        "side": side,
+        "leverage": 1.0,
+    }
+    if not error:
+        order = exchange.create_stoploss(**params)
+        assert isinstance(order, dict)
+        assert order.get("ft_order_type") == "stoploss"
+        assert order["status"] == "open"
+        # assert order["price"] == price
+    else:
+        with pytest.raises(InvalidOrderException, match=r".*Stoploss would trigger immediately.*"):
+            exchange.create_stoploss(**params)
+
+
 @pytest.mark.parametrize(
     "side,rate,amount,endprice",
     [