Mockito 단위 테스트

@ExtendWith(MockitoExtension.class)
class OrderServiceTest {
    @InjectMocks OrderService orderService;
    @Mock OrderRepository orderRepository;
    @Mock PaymentService paymentService;
    @Mock EmailService emailService;
    @Captor ArgumentCaptor<Order> orderCaptor;

    @Test
    @DisplayName("주문 생성 — 결제 성공 후 이메일 발송")
    void createOrder_Success() {
        // given
        User user = new User(1L, "test@test.com");
        CreateOrderDto dto = new CreateOrderDto(List.of(1L, 2L), 50000);
        when(paymentService.pay(50000)).thenReturn(true);
        when(orderRepository.save(any(Order.class)))
            .thenAnswer(inv -> inv.getArgument(0));

        // when
        OrderDto result = orderService.create(user, dto);

        // then
        assertThat(result).isNotNull();
        verify(orderRepository).save(orderCaptor.capture());
        Order savedOrder = orderCaptor.getValue();
        assertThat(savedOrder.getTotal()).isEqualTo(50000);
        verify(emailService, times(1))
            .sendOrderConfirmation(eq("test@test.com"), any());
    }

    @Test
    @DisplayName("결제 실패 시 주문 저장 안 됨")
    void createOrder_PaymentFail() {
        when(paymentService.pay(anyInt())).thenReturn(false);
        assertThatThrownBy(() -> orderService.create(user, dto))
            .isInstanceOf(PaymentFailException.class);
        verify(orderRepository, never()).save(any());
    }
}