Test 5s offset on since

tests/data/test_history.py

@@ -548,6 +548,17 @@ def test_download_trades_history(trades_history, mocker, default_conf, testdatad
     assert file1.is_file()
 
     # clean files freshly downloaded
+    _clean_test_file(file1)
+    ght_mock.reset_mock()
+    since_time = int(trades_history[-2][0] // 1000)
+    timerange = TimeRange('date', None, since_time, 0)
+    assert _download_trades_history(data_handler=data_handler, exchange=exchange,
+                                    pair='ETH/BTC', timerange=timerange)
+
+    assert ght_mock.call_count == 1
+    # Check this in seconds - since we had to convert to seconds above too.
+    assert int(ght_mock.call_args_list[0].kwargs['since'] // 1000) == since_time - 5
+
     _clean_test_file(file1)
 
     mocker.patch('freqtrade.exchange.Exchange.get_historic_trades',