Mockito is a Java mocking framework and JUnit testing library used to create simulated objects and stub method calls to isolate components during unit tests. It functions as a dynamic proxy generator and bytecode instrumentation tool, allowing for the creation of runtime substitutes that mimic the behavior of real classes.
The framework distinguishes itself by providing the ability to mock final classes and methods, bypassing standard language restrictions through bytecode modification. This capability enables the testing of legacy code that lacks interfaces.
The toolset covers behavioral mocking to define specific method responses and interaction verification to ensure methods were called with the correct arguments. It provides mechanisms for mock object generation and the recording of method interaction history for post-execution verification.
