Starter Kit: Unit Testing in TakeTwo repositories

### Background on the problem the feature will solve/improved user experience
Our code currently lacks unit testing, which is needed for test driven development practices: easy debugging, functional testing, etc.

### Describe the solution you'd like
Provide unit tests for various TakeTwo repositories:

- [ ] https://github.com/Call-for-Code-for-Racial-Justice/TakeTwo-Marker-ChromeExtension
- [ ] https://github.com/Call-for-Code-for-Racial-Justice/TakeTwo-DataScience/
- [ ] https://github.com/Call-for-Code-for-Racial-Justice/taketwo-webapi/

### Tasks
- [ ] research existing tests of similar code bases
- [ ] document list of tests to be implemented for each repository based on programming language, architecture, etc
- [ ] create Github issues for each test in the appropriate repo and link to this issue as well
- [ ] implement changes in each repository as appropriate

### Acceptance Criteria

- [ ] At least 60% code coverage by unit tests

まず、リンクされている3つのリポジトリ、TakeTwo-Marker-ChromeExtension、TakeTwo-DataScience、taketwo-webapiと、比較可能なcodebaseに存在するテストを確認します。各リポジトリに必要なテストを文書化し、適切なリポジトリにリンクされたissueを作成して、それらのissueで実装を追跡します。各リポジトリに計画したunit testがあり、作業全体で少なくとも60%のcode coverageに達すれば完了です。

索引モデルが issue の本文から書いたものです。