test: Add test with faulty behavior

part of #11074

freqtrade/plugins/pairlist/PercentChangePairList.py

@@ -191,7 +191,6 @@ class PercentChangePairList(IPairList):
                     for k, v in tickers.items()
                     if (
                         self._exchange.get_pair_quote_currency(k) == self._stake_currency
-                        and (self._use_range or v.get("percentage") is not None)
                         and v["symbol"] in _pairlist
                     )
                 ]

tests/conftest.py

@@ -2237,7 +2237,7 @@ def tickers():
                 "first": None,
                 "last": 8603.67,
                 "change": -0.879,
-                "percentage": None,
+                "percentage": -8.95,
                 "average": None,
                 "baseVolume": 30414.604298,
                 "quoteVolume": 259629896.48584127,
@@ -2281,7 +2281,7 @@ def tickers():
                 "first": None,
                 "last": 129.28,
                 "change": 1.795,
-                "percentage": None,
+                "percentage": -2.5,
                 "average": None,
                 "baseVolume": 59698.79897,
                 "quoteVolume": 29132399.743954,

tests/plugins/test_percentchangepairlist.py

@@ -360,9 +360,15 @@ def test_gen_pairlist_from_tickers(mocker, rpl_config, tickers):
     exchange = get_patched_exchange(mocker, rpl_config, exchange="binance")
     pairlistmanager = PairListManager(exchange, rpl_config)
 
-    remote_pairlist = PercentChangePairList(
-        exchange, pairlistmanager, rpl_config, rpl_config["pairlists"][0], 0
-    )
+    remote_pairlist = pairlistmanager._pairlist_handlers[0]
+
+    # The generator returns BTC ETH and TKN - filtering the first ensures removing pairs in this step ain't problematic.
+    def _validate_pair(pair, ticker):
+        if pair == "BTC/USDT":
+            return False
+        return True
+
+    remote_pairlist._validate_pair = _validate_pair
 
     result = remote_pairlist.gen_pairlist(tickers.return_value)