What are JUnit 5 lifecycle annotations (@BeforeEach, @BeforeAll, @AfterEach, @AfterAll)? JUnit 5 लाइफसाइकल एनोटेशन (@BeforeEach, @BeforeAll, @AfterEach, @AfterAll) क्या हैं?

@BeforeEach runs before every individual test method, typically used to reset test data or re-create mocks so tests don't leak state between each other. @AfterEach runs after every test method, used for cleanup like closing resources.

@BeforeAll runs once before all tests in the class (must be static unless the test class uses @TestInstance(Lifecycle.PER_CLASS)), suited for expensive one-time setup like starting a shared Testcontainer. @AfterAll runs once after all tests complete, used for expensive teardown. Choosing the right scope avoids both redundant setup cost and unwanted state leaking between tests.

class OrderServiceTest {
    @BeforeAll
    static void setupOnce() { /* start shared resource */ }

    @BeforeEach
    void setup() { orderService = new OrderService(mockGateway); }

    @AfterEach
    void tearDown() { reset(mockGateway); }
}