def METHOD_NAME(self):
    database = {
        "users": [
            {"name": "Adam", "owes": {"Bob": 3.0}, "owed_by": {}, "balance": -3.0},
            {"name": "Bob", "owes": {}, "owed_by": {"Adam": 3.0}, "balance": 3.0},
        ]
    }
    api = RestAPI(database)
    payload = json.dumps({"lender": "Adam", "borrower": "Bob", "amount": 2.0})
    response = api.post("/iou", payload)
    expected = {
        "users": [
            {"name": "Adam", "owes": {"Bob": 1.0}, "owed_by": {}, "balance": -1.0},
            {"name": "Bob", "owes": {}, "owed_by": {"Adam": 1.0}, "balance": 1.0},
        ]
    }
    self.assertDictEqual(json.loads(response), expected)