Unit testing is a software testing method by which individual units of source code are tested to determine if they are fit for use. A unit is the smallest testable part of an application like functions, classes, procedures, interfaces, etc. In procedural programming, a unit may be an individual program, function, procedure, or even a single line of code. In object-oriented programming (OOP), the smallest unit is a method, which may belong to a base/ super class or abstract class, or derived/ child class.
Here are 12 best Java Unit Testing Open Source libraries in 2022 including mockito - popular Mocking framework for unit tests written; powermock - Java framework for unit testing; ArchUnit - a free, simple and extensible library for checking the architecture of your Java code.