Unit test compensation models

* adds unit tests for compensation models
* removes duplicated unit tests

intervention/models/intervention.py

@@ -419,8 +419,11 @@ class InterventionDocument(AbstractDocument):
             # The only file left for this intervention is the one which is currently processed and will be deleted
             # Make sure that the intervention folder itself is deleted as well, not only the file
             # Therefore take the folder path from the file path
-            folder_path = self.file.path.split("/")[:-1]
-            folder_path = "/".join(folder_path)
+            try:
+                folder_path = self.file.path.split("/")[:-1]
+                folder_path = "/".join(folder_path)
+            except ValueError:
+                folder_path = None
 
         if user:
             self.instance.mark_as_edited(user, edit_comment=DOCUMENT_REMOVED_TEMPLATE.format(self.title))