According to instruction, response of /users is {"users":<List of all User objects>}.
Therefore, I thought it is something like {"users":[{"name":"Bob","owes":{},"owed_by":{},"balance":0}]}.
However, the test expects [{"name":"Bob","owes":{},"owed_by":{},"balance":0}].
If the test expects this string, the description for response of /users/ should be [<List of all User objects>].
According to instruction, it is possible to have both owes and owed_by for same person.
However, test case Lender_owes_borrower expects that owes and owed_by for same person should canceled out each other.