Unit tests are isolated from the rest of the codebase, which helps them to be fast to run, simple to write, and easy to understand and maintain.

How can I motivate coworkers to write unit tests? Making a dreary but important task commonplace will require some creativity.

I assume that my project is decoupled enough to allow for unit testing. But how big exactly, in terms of clases and functions, does my project need to be to make unit testing worthwhile?