Make candle_limit optionally timeframe dependent

tests/exchange/test_ccxt_compat.py

@@ -5,11 +5,14 @@ However, these tests should give a good idea to determine if a new exchange is
 suitable to run with freqtrade.
 """
 
+from datetime import datetime, timedelta, timezone
+from freqtrade.exchange.exchange import timeframe_to_minutes
 from pathlib import Path
 
 import pytest
 
 from freqtrade.resolvers.exchange_resolver import ExchangeResolver
+from freqtrade.exchange import timeframe_to_prev_date
 from tests.conftest import get_default_conf
 
 
@@ -122,7 +125,10 @@ class TestCCXTExchange():
         assert len(ohlcv[pair_tf]) == len(exchange.klines(pair_tf))
         # assert len(exchange.klines(pair_tf)) > 200
         # Assume 90% uptime ...
-        assert len(exchange.klines(pair_tf)) > exchange._ohlcv_candle_limit * 0.90
+        assert len(exchange.klines(pair_tf)) > exchange.ohlcv_candle_limit(timeframe) * 0.90
+        # Check if last-timeframe is within the last 2 intervals
+        now = datetime.now(timezone.utc) - timedelta(minutes=(timeframe_to_minutes(timeframe) * 2))
+        assert exchange.klines(pair_tf).iloc[-1]['date'] >= timeframe_to_prev_date(timeframe, now)
 
     # TODO: tests fetch_trades (?)