Add unit testing for REST API

[ahiijny]

I think probably this would be considered more "integration testing" rather than "unit testing". The terminology is a bit confusing though (there's also "functional testing", "end-to-end testing", "acceptance testing", etc.?...)

What should the folder structure for these tests be? Since they're testing at a different level than the present unit tests, I think it would be better if they were separated in some way.

Some ideas I found online:

• Separate top-level folders: https://stackoverflow.com/questions/42491138/node-js-folder-structure-unit-tests-and-e2e-tests
• Separate unit and integration subfolders inside the test folder: https://stackoverflow.com/questions/37605811/separation-of-unit-tests-and-integration-tests
• Pros and cons of keeping the source files with test files in the same directory vs. separating src and test entirely: https://www.reddit.com/r/node/comments/4ipcam/what_is_the_directory_structure_that_you_use_for

Also somewhat relevant:

• How to organize tests into smaller, more manageable parts: https://stackoverflow.com/questions/20548723/how-do-you-structure-your-tests-for-your-server-applications-in-node-js
• Folder structure for a Node.js project: https://stackoverflow.com/questions/5178334/folder-structure-for-a-node-js-project

I'm assuming that adding unnecessary additional dependencies would be unwanted, so mocha + chai will be used for this as well? Then, some possibly helpful resources:

• Testing Node API with Mocha & Chai: https://dev.to/easybuoy/testing-node-api-with-mocha-chai-248b
• Tutorial: How to Write Integration Tests for REST APIs with node.js: https://maximilianschmitt.me/posts/tutorial-rest-api-integration-testing-node-js/
• Test a Node RESTful API with Mocha and Chai: https://scotch.io/tutorials/test-a-node-restful-api-with-mocha-and-chai