Improve test coverage

tests/data/test_btanalysis.py

@@ -13,7 +13,8 @@ from freqtrade.data.btanalysis import (BT_DATA_COLUMNS, analyze_trade_parallelis
                                        calculate_underwater, combine_dataframes_with_mean,
                                        create_cum_profit, extract_trades_of_period,
                                        get_latest_backtest_filename, get_latest_hyperopt_file,
-                                       load_backtest_data, load_trades, load_trades_from_db)
+                                       load_backtest_data, load_backtest_metadata, load_trades,
+                                       load_trades_from_db)
 from freqtrade.data.history import load_data, load_pair_history
 from freqtrade.exceptions import OperationalException
 from tests.conftest import create_mock_trades
@@ -40,7 +41,7 @@ def test_get_latest_backtest_filename(testdatadir, mocker):
         get_latest_backtest_filename(testdatadir)
 
 
-def test_get_latest_hyperopt_file(testdatadir, mocker):
+def test_get_latest_hyperopt_file(testdatadir):
     res = get_latest_hyperopt_file(testdatadir / 'does_not_exist', 'testfile.pickle')
     assert res == testdatadir / 'does_not_exist/testfile.pickle'
 
@@ -51,6 +52,17 @@ def test_get_latest_hyperopt_file(testdatadir, mocker):
     assert res == testdatadir.parent / "hyperopt_results.pickle"
 
 
+def test_load_backtest_metadata(mocker, testdatadir):
+    res = load_backtest_metadata(testdatadir / 'nonexistant.file.json')
+    assert res == {}
+
+    mocker.patch('freqtrade.data.btanalysis.get_backtest_metadata_filename')
+    mocker.patch('freqtrade.data.btanalysis.json_load', side_effect=Exception())
+    with pytest.raises(OperationalException,
+                       match=r"Unexpected error.*loading backtest metadata\."):
+        load_backtest_metadata(testdatadir / 'nonexistant.file.json')
+
+
 def test_load_backtest_data_old_format(testdatadir, mocker):
 
     filename = testdatadir / "backtest-result_test222.json"