refining CountryColumnsMergerTest

src/CountryColumnsMerger.py

@@ -7,7 +7,7 @@ class CountryColumnsMerger:
     def mergeCountryColumnOfSrcIntoDst(src: pd.DataFrame, dst: pd.DataFrame):
         merged = pd.merge(
             dst,
-            src,
+            CountryColumnsMerger._drop_duplicates(src['COUNTRY']),
             how = 'left',
             left_index = True,
             right_index = True,
@@ -21,10 +21,14 @@ class CountryColumnsMerger:
                                 .astype('string'))
         return merged.drop(columns = ['COUNTRY_dst', 'COUNTRY_src'])
     
+    @staticmethod
+    def _drop_duplicates(df):
+        return df[~df.index.duplicated(keep = 'first')]
+
     @staticmethod
     def _mergeSrcIntoDst(src, dst):
-        if (CountryColumnsMerger._notEqual(src, dst)) or (pd.isnull(src) and pd.isnull(dst)):
-            raise Exception()        
+        if CountryColumnsMerger._notEqual(src, dst):
+            raise Exception(f'{src} != {dst}')        
         
         if pd.isnull(dst) and not pd.isnull(src):
             return src