Agile automated testing (Black Box unit testing)

? If a unit test is performed for specific code implementations, the unit test code that is written will be changed as required, and it needs to be changed frequently, does unit test code cost too much?

? Unit tests should emphasize the intention and interfaces of external users (systems) to write tests and perform so-called black box tests? In this way, the unit test code written will be relatively strong, better able to adapt to changes in demand?

? This article uses JUnit and mockito to write unit tests of the black box to drive design and development, thus improving the efficiency and quality of software development?

Attachment: Agile automated testing (Black Box unit testing)