This test class can be described as follows:

@ExtendWith(MockitoExtension.class): Mockito’s JUnit 5 hook to mock out any fields with the @Mock annotation

VideoService: The class under test

VideoRepository: A collaborator required for VideoService is marked for mocking

@BeforeEach: JUnit 5’s annotation to make this setup method run before every test method

The setUp() method shows VideoService being created with the mock VideoRepository injected through its constructor