Documentation: How to do unit testing

What are you trying to accomplish?

I'm building a web server using Diesel. I want to unit test my code that access the DB via diesel. But I'm finding it unclear how to do this.

What is the expected output?

A documentation guide that explain best practices for unit testing while using Diesel and how to.

For example if I choose to hit the DB, how to clean it before each test, or run tests in transactions. Maybe something about factories.

If I would like to mock db call, how to achieve this.