test for Handle stop on exchange partial filled

part of #8374

tests/test_freqtradebot.py

@@ -1290,6 +1290,64 @@ def test_handle_stoploss_on_exchange(mocker, default_conf_usdt, fee, caplog, is_
     assert trade.exit_reason == str(ExitType.EMERGENCY_EXIT)
 
 
+@pytest.mark.parametrize("is_short", [False, True])
+def test_handle_stoploss_on_exchange_partial(
+        mocker, default_conf_usdt, fee, is_short, limit_order) -> None:
+    stop_order_dict = {'id': "101", "status": "open"}
+    stoploss = MagicMock(return_value=stop_order_dict)
+    enter_order = limit_order[entry_side(is_short)]
+    exit_order = limit_order[exit_side(is_short)]
+    patch_RPCManager(mocker)
+    patch_exchange(mocker)
+    mocker.patch.multiple(
+        EXMS,
+        fetch_ticker=MagicMock(return_value={
+            'bid': 1.9,
+            'ask': 2.2,
+            'last': 1.9
+        }),
+        create_order=MagicMock(side_effect=[
+            enter_order,
+            exit_order,
+        ]),
+        get_fee=fee,
+        create_stoploss=stoploss
+    )
+    freqtrade = FreqtradeBot(default_conf_usdt)
+    patch_get_signal(freqtrade, enter_short=is_short, enter_long=not is_short)
+
+    freqtrade.enter_positions()
+    trade = Trade.session.scalars(select(Trade)).first()
+    trade.is_short = is_short
+    trade.is_open = True
+    trade.open_order_id = None
+    trade.stoploss_order_id = None
+
+    assert freqtrade.handle_stoploss_on_exchange(trade) is False
+    assert stoploss.call_count == 1
+    assert trade.stoploss_order_id == "101"
+    assert trade.amount == 30
+    stop_order_dict.update({'id': "102"})
+    # Stoploss on exchange is cancelled on exchange, but filled partially.
+    # Must update trade amount to guarantee successful exit.
+    stoploss_order_hit = MagicMock(return_value={
+        'id': "101",
+        'status': 'canceled',
+        'type': 'stop_loss_limit',
+        'price': 3,
+        'average': 2,
+        'filled': trade.amount / 2,
+        'remaining': trade.amount / 2,
+        'amount': enter_order['amount'],
+    })
+    mocker.patch(f'{EXMS}.fetch_stoploss_order', stoploss_order_hit)
+    assert freqtrade.handle_stoploss_on_exchange(trade) is False
+    # Stoploss filled partially ...
+    assert trade.amount == 15
+
+    assert trade.stoploss_order_id == "102"
+
+
 @pytest.mark.parametrize("is_short", [False, True])
 def test_handle_sle_cancel_cant_recreate(mocker, default_conf_usdt, fee, caplog, is_short,
                                          limit_order) -> None: