Correctly handle identical timerame merges

tests/strategy/test_strategy_helpers.py

@@ -28,7 +28,7 @@ def test_merge_informative_pair():
     data = generate_test_data('15m', 40)
     informative = generate_test_data('1h', 40)
 
-    result = merge_informative_pair(data, informative, '1h', ffill=True)
+    result = merge_informative_pair(data, informative, '15m', '1h', ffill=True)
     assert isinstance(result, pd.DataFrame)
     assert len(result) == len(data)
     assert 'date' in result.columns
@@ -59,3 +59,30 @@ def test_merge_informative_pair():
     assert result.iloc[7]['date_1h'] == result.iloc[0]['date']
     # Next 4 rows contain the next Hourly date original date row 4
     assert result.iloc[8]['date_1h'] == result.iloc[4]['date']
+
+
+def test_merge_informative_pair_same():
+    data = generate_test_data('15m', 40)
+    informative = generate_test_data('15m', 40)
+
+    result = merge_informative_pair(data, informative, '15m', '15m', ffill=True)
+    assert isinstance(result, pd.DataFrame)
+    assert len(result) == len(data)
+    assert 'date' in result.columns
+    assert result['date'].equals(data['date'])
+    assert 'date_15m' in result.columns
+
+    assert 'open' in result.columns
+    assert 'open_15m' in result.columns
+    assert result['open'].equals(data['open'])
+
+    assert 'close' in result.columns
+    assert 'close_15m' in result.columns
+    assert result['close'].equals(data['close'])
+
+    assert 'volume' in result.columns
+    assert 'volume_15m' in result.columns
+    assert result['volume'].equals(data['volume'])
+
+    # Dates match 1:1
+    assert result['date_15m'].equals(result['date'])