CLONE - A teacher can choose whether to allow resubmitting of assignments

1. Login as a teacher, update an 'Upload a single file' assignment and set 'Allow resubmitting' to Yes.
2. Login as a student and upload a file.
3. Login as a teacher and give the student's submission a grade and comment.
4. Login as a student and check that the submission grade and comment are displayed, and that a further file can be uploaded.