fix test and docstring

Author: JavierCladellas

src/feelpp/benchmarking/report/transformationFactory.py

@@ -16,16 +16,15 @@ def calculate(self,df):
     @staticmethod
     def chooseColumn(value,df):
         """ Chooses a column from a list of possible columns splitted by '|' from a dataframe, returns the first occurence in the dataframe.
-            If no column is found, returns None
-            If the value is null (0, False, None, ...), returns None
+            IF the value is null (0, False, None, ...) or not found, returns None
         Args:
             value (str): The string containing the possible columns, splitted by '|'. e.g. "column1|column2|column3"
             df (pd.DataFrame): The dataframe where the columns are searched
         Returns:
             str: The first column found in the dataframe, or None
         """
         if not value:
-            return value
+            return None
 
         possible_columns = value.split("|")
         for column in possible_columns:

tests/report/test_transformationFactory.py

@@ -112,7 +112,7 @@ def test_speedupStrategy(self):
         ("non_existent|param2","param2"),
         ("non_existent|param2|param3","param2"),
         ("non_existent",None),
-        (0,0), (None,None), (False,None),
+        (0,None), (None,None), (False,None),
     ])
     def test_chooseColumn(self,param_names,expected):
         df = pd.DataFrame(columns=["param1","param2","param3","param4"])