Add some safety measures for new startup_candles verification

freqtrade/exchange/exchange.py

@@ -622,7 +622,8 @@ class Exchange:
 
         candle_limit = self.ohlcv_candle_limit(
             timeframe, self._config['candle_type_def'],
-            date_minus_candles(timeframe, startup_candles))
+            int(date_minus_candles(timeframe, startup_candles).timestamp() * 1000)
+            if timeframe else None)
         # Require one more candle - to account for the still open candle.
         candle_count = startup_candles + 1
         # Allow 5 calls to the exchange per pair

freqtrade/exchange/okx.py

@@ -1,5 +1,4 @@
 import logging
-from datetime import datetime, timedelta, timezone
 from typing import Dict, List, Optional, Tuple
 
 import ccxt

tests/exchange/test_exchange.py

@@ -939,6 +939,7 @@ def test_validate_timeframes_emulated_ohlcvi_2(default_conf, mocker):
 
 
 def test_validate_timeframes_not_in_config(default_conf, mocker):
+    # TODO: this test does not assert ...
     del default_conf["timeframe"]
     api_mock = MagicMock()
     id_mock = PropertyMock(return_value='test_exchange')
@@ -954,6 +955,7 @@ def test_validate_timeframes_not_in_config(default_conf, mocker):
     mocker.patch('freqtrade.exchange.Exchange.validate_pairs')
     mocker.patch('freqtrade.exchange.Exchange.validate_stakecurrency')
     mocker.patch('freqtrade.exchange.Exchange.validate_pricing')
+    mocker.patch('freqtrade.exchange.Exchange.validate_required_startup_candles')
     Exchange(default_conf)