java void方法单测断言的三种实现示例

@Test
void reset_shouldClearCounter() {
    Counter counter = new Counter();
    counter.increment(); // 初始值+1
    
    // 执行 void 方法
    counter.reset();
    
    // 验证内部状态
    assertEquals(0, counter.getCount());
    
    // 使用 AssertJ 更优雅的断言
    assertThat(counter.getCount()).isZero();
}

@Test
void notifyUser_shouldTriggerNotificationService() {
    // 创建依赖项的 mock
    NotificationService mockService = mock(NotificationService.class);
    UserService userService = new UserService(mockService);
    
    // 执行 void 方法
    userService.notifyUser("user123");
    
    // 验证是否调用了依赖对象的特定方法
    verify(mockService).sendNotification(eq("user123"));
    
    // 验证调用次数
    verify(mockService, times(1)).sendNotification(any());
}

@Test
void withdraw_shouldThrowExceptionWhenOverdraft() {
    Account account = new Account(100);
    
    // 验证异常断言 (JUnit 5)
    assertThrows(InsufficientFundsException.class, () -> {
        account.withdraw(200); // void 方法
    });
    
    // AssertJ 异常断言
    assertThatThrownBy(() -> account.withdraw(200))
        .isInstanceOf(InsufficientFundsException.class)
        .hasMessage("余额不足");
}

@Test
void updateProfile_shouldChangeMultipleFields() {
    User user = new User();
    user.updateProfile("Alice", 30, "alice@email.com");
    
    // 自定义断言方法
    assertUserProfile(user, "Alice", 30, "alice@email.com");
}
 
private void assertUserProfile(User user, String name, int age, String email) {
    assertThat(user.getName()).isEqualTo(name);
    assertThat(user.getAge()).isEqualTo(age);
    assertThat(user.getEmail()).isEqualTo(email);
}

public class ShoppingCartTest {
    @Test
    void clear_shouldRemoveAllItems() {
        // 准备
        ShoppingCart cart = new ShoppingCart();
        cart.addItem(new Item("Book", 15.99));
        cart.addItem(new Item("Pen", 1.99));
        
        // 执行
        cart.clear();
        
        // 验证
        assertThat(cart.isEmpty())
            .as("购物车应在清空后为空")
            .isTrue();
    }
 
    @Test
    void processOrder_shouldPersistToDatabase() {
        // 准备
        OrderDao mockDao = mock(OrderDao.class);
        OrderService service = new OrderService(mockDao);
        Order order = new Order("ORDER-123");
        
        // 执行
        service.processOrder(order);
        
        // 验证数据库交互
        verify(mockDao).save(order);
    }
 
    @Test
    void setDiscount_shouldThrowForInvalidValue() {
        Product product = new Product();
        
        assertThatThrownBy(() -> product.setDiscount(-10))
            .isInstanceOf(IllegalArgumentException.class)
            .hasMessageContaining("折扣值非法");
    }
}