Testing Pyramid

Structure

Unit Tests         — fast, no Spring context, mock dependencies    (70%)
Slice Tests        — partial Spring context (@WebMvcTest, @DataJpaTest) (20%)
Integration Tests  — full context + real DB via Testcontainers     (10%)

Unit Tests — Services

@ExtendWith(MockitoExtension.class)
class OrderServiceTest {

    @Mock private OrderRepository orderRepository;
    @Mock private InventoryService inventoryService;