JUnit 5 Annotations | Java Fresher Interview

Direct Answer

Core Jupiter annotations include @Test, @BeforeEach/@AfterEach, @BeforeAll/@AfterAll, @DisplayName, @Disabled, and @Nested. Before-all and after-all methods are normally static under the default per-method lifecycle; @TestInstance(PER_CLASS) permits instance methods. A disabled reason is optional in the API but valuable in reports.

Code Example

class OrderServiceTest {
    private OrderService orderService;

    @BeforeAll
    static void initShared() {           // static under default PER_METHOD lifecycle
        System.out.println("start suite");
    }
    @BeforeEach
    void setUp() {                        // before each test invocation
        orderService = new OrderService(new InMemoryRepo());
    }
    @Test
    @DisplayName("applies 10% discount for premium customers")
    void appliesPremiumDiscount() {
        assertEquals(90.0, orderService.priceFor(premium(), 100.0));
    }
    @Test
    @Disabled("flaky until clock is injected — see TICKET-123")
    void expiresAtMidnight() { }
    @AfterEach
    void tearDown() { orderService.close(); }   // after each invocation
    @AfterAll
    static void cleanup() { System.out.println("end suite"); }
}

Common Mistakes & Pitfalls

• @BeforeAll not static under the default lifecycle. With PER_METHOD, a once-per-class hook is normally static; @TestInstance(PER_CLASS) permits an instance method.
• Confusing Each vs All. @BeforeEach runs before each test invocation; @BeforeAll runs once for the container. Put setup at the scope where it belongs.
• @Disabled with no explanation. The reason is optional, but a useful reason keeps the report actionable.
• Mixing JUnit generations accidentally. Jupiter uses @BeforeEach/@AfterEach; JUnit 4 uses @Before/@After and needs the Vintage engine when run on the Platform.