Software Architect's Handbook

What are unit tests?

Unit testing is the practice of testing the smallest testable units of a software system, such as methods, to ensure that they are working properly. It plays an important role in increasing the quality of your software. Functionality in a software system is decomposed into discrete, testable behaviors that are then tested as units.

Some of the principles we have discussed, such as creating loosely coupled code, following principles such as DRY, SoC, and single responsibility, and using techniques such as DI, create code that is independent and decoupled from dependencies. These qualities make our code testable and allow us to focus a unit test on a single unit.