Add integration tests for database

[matthew-white]

From our call today, it sounds like we want to add integration tests in addition to unit tests for the database. This issue is to add those integration tests: #10 encompasses only unit tests.

As part of this, I think we should create a test database?

[issa-tseng]

I'm not sure what this means. An integration test necessarily tests more than a single component, and a database is a single component.