What are the differences between Mockito, JUnit, and AssertJ libraries in testing?

Mockito is a library for creating mock objects that simulate the behavior of real dependencies in tests. It allows replacing real objects with stubs to isolate the tested code.

JUnit is a framework for writing and running unit tests in Java. It provides annotations and mechanisms for organizing tests, as well as tools for verifying their success.

AssertJ is a library for convenient and expressive writing of assertions in tests. It extends the standard capabilities of JUnit, allowing for readable and chainable checks.

In summary:

• JUnit is a framework for running tests and organizing the testing process.
• Mockito is for creating and configuring mock objects to isolate the tested code.
• AssertJ provides convenient and expressive assertions for verifying test results.