Actual Unit tests

Lord how annoying it is to write tests, but this application and it's importance requires some basic unit tests. We should have edge cases tested against.

- Underclassman tries to sign as upperclassman
- Off Floor Underclassman tries to sign packet

We will also need some kind of mocking database system to create the logic for this

首先定位以下两个所列案例的应用逻辑：一名以upperclassman身份签名的underclassman，以及一名签署packet的off-floor underclassman。然后确定数据库访问是如何处理的，并选择一种mocking方法；当两个edge case都有unit test覆盖，并且测试能够在不使用真实数据库的情况下可靠运行时，即视为完成。

由索引模型根据 Issue 内容生成。