develop some unit tests

[arlin]

As a precursor to implementing CI (in pursuit of our goal of implementing this on as many repos as possible), develop a minimal test suite.

For now, just focus on unit tests that do not depend on external services.

[ducvan0212]

I created a test suite. The test can be run by command

rails test

or

rails test <file>

The test is available at /test folder in dev repo.

I am not sure how much test should be enough, so I will just leave the issue in in_progress label