junit-mockito-patterns
JUnit5 + Mockito 测试框架技能。覆盖 JUnit5 @ExtendWith替代@RunWith、Mockito @Mock/@InjectMocks规则、测试隔离原则(FIRST)、@SpringBootTest何时用何时不用(@WebMvcTest/@DataJpaTest切片测试)、BDDMockito given/willReturn风格、ArgumentCaptor参数捕获、verify行为验证、@ParameterizedTest参数化测试。 当用户编写 Java 单元测试/集成测试、Mock外部依赖时需要此技能。
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/full-stack-skills/java-skills --skill junit-mockito-patterns- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads junit-mockito-patterns automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
JUnit5 + Mockito 测试规则
来源：https://junit.org/junit5/docs/current/user-guide/
Mockito：https://javadoc.io/doc/org.mockito/mockito-core/latest/org/mockito/Mockito.html
Capability Boundaries
✅ Strong Suits
- JUnit5 迁移规则 — @ExtendWith 替代 @RunWith, @Test 导入 org.junit.jupiter.api
- Mockito 规则 — @Mock(外部依赖) + @InjectMocks(被测试对象), 不 Mock POJO
- 测试隔离(FIRST原则) — Fast/Independent/Repeatable/Self-Validating/Timely
- 切片测试 — @WebMvcTest(Controller) / @DataJpaTest(Repository) / @JsonTest
- BDD风格 — BDDMockito.given()/willReturn()/then().should() 替代 when/thenReturn/verify
- 行为验证 — verify() + ArgumentCaptor
- @ParameterizedTest + @MethodSource — 参数化测试简化多场景
- @Nested 分组 — 组织相关测试场景
❌ Out of Scope
- 集成测试/端到端测试 → Playwright/Selenium（已有技能）
- 性能测试 → JMH（Java Microbenchmark Harness）
JUnit4 → JUnit5 迁移对照
| JUnit4 | JUnit5 | 说明 |
|---|---|---|
@RunWith(SpringRunner.class) | @ExtendWith(SpringExtension.class) | 扩展机制 |
@RunWith(MockitoJUnitRunner.class) | @ExtendWith(MockitoExtension.class) | Mockito扩展 |
@Test(expected = Exception.class) | assertThrows(Exception.class, () -> {...}) | 异常断言 |
@Before | @BeforeEach | 每个测试前执行 |
@After | @AfterEach | 每个测试后执行 |
@BeforeClass | @BeforeAll | 所有测试前(static) |
@AfterClass | @AfterAll | 所有测试后(static) |
@Ignore | @Disabled | 禁用测试 |
@FixMethodOrder | @TestMethodOrder(MethodName) | 测试顺序 |
LLM最常犯的错误
| # | 错误 | 正确做法 |
|---|---|---|
| 1 | import org.junit.Test (JUnit4) | import org.junit.jupiter.api.Test (JUnit5) |
| 2 | @RunWith(MockitoJUnitRunner.class) | @ExtendWith(MockitoExtension.class) |
| 3 | 测试 Service 用 @SpringBootTest 启动整个上下文 | 用 @ExtendWith(MockitoExtension.class) 纯 Mockito |
| 4 | Controller 测试启动整个应用 | @WebMvcTest + @MockBean 只加载 Controller 层 |
| 5 | Mock 值对象(POJO/DTO) | 只 Mock 外部依赖(DB/HTTP/MQ)，POJO 直接 new |
| 6 | verify(mock, never()) 不写 times(0) | verify(mock, never()).method() 或 verify(mock, times(0)).method() |
| 7 | 每个测试方法都 initMocks(this) | @ExtendWith 自动初始化 |
| 8 | 用 when().thenReturn() (非BDD) | BDD 风格: given().willReturn() |
| 9 | @SpringBootTest 做单元测试(慢，3s+) | 切片测试 < 200ms |
| 10 | 不写 @DisplayName | 测试方法中文描述，方便定位 |
核心规则速查
纯单元测试（推荐）
@ExtendWith(MockitoExtension.class)
@DisplayName("用户服务测试")
class UserServiceTest {
@Mock UserRepository userRepo; // 外部依赖
@Mock CacheManager cacheManager;
@InjectMocks UserService userService; // 被测试对象(构造器注入)
@Test
@DisplayName("查询用户-缓存命中-直接返回")
void getUser_CacheHit_ReturnFromCache() {
// given(BDD风格)
User cached = new User(1L, "zhang");
given(cacheManager.get("user:1")).willReturn(cached);
// when
User result = userService.getUser(1L);
// then
assertThat(result.getName()).isEqualTo("zhang");
then(userRepo).should(never()).findById(anyLong()); // BDD验证
}
@Test
@DisplayName("查询用户-未命中-查DB并缓存")
void getUser_CacheMiss_QueryDBAndCache() {
// given
given(cacheManager.get("user:1")).willReturn(null);
given(userRepo.findById(1L)).willReturn(Optional.of(new User(1L, "zhang")));
// when
User result = userService.getUser(1L);
// then
assertThat(result).isNotNull();
then(cacheManager).should().set(eq("user:1"), any(User.class));
}
}
Controller 切片测试
@WebMvcTest(UserController.class)
@DisplayName("用户控制器测试")
class UserControllerTest {
@Autowired MockMvc mockMvc;
@MockBean UserService userService;
@Test
@DisplayName("GET /user/1 返回用户信息")
void getUser_ById_ReturnsUser() throws Exception {
given(userService.getUser(1L)).willReturn(new UserVO(1L, "zhang"));
mockMvc.perform(get("/user/1"))
.andExpect(status().isOk())
.andExpect(jsonPath("$.username").value("zhang"));
}
@Test
@DisplayName("GET /user/1 用户不存在返回404")
void getUser_NotFound_Returns404() throws Exception {
given(userService.getUser(99L)).willThrow(new UserNotFoundException(99L));
mockMvc.perform(get("/user/99"))
.andExpect(status().isNotFound());
}
}
Repository 切片测试
@DataJpaTest
@DisplayName("用户仓库测试")
class UserRepositoryTest {
@Autowired TestEntityManager em;
@Autowired UserRepository repo;
@Test
@DisplayName("按用户名查询-存在-返回用户")
void findByUsername_Exists_ReturnUser() {
em.persistAndFlush(new User("zhang", "zhang@test.com"));
Optional<User> result = repo.findByUsername("zhang");
assertThat(result).isPresent();
assertThat(result.get().getEmail()).isEqualTo("zhang@test.com");
}
@Test
@DisplayName("按用户名查询-不存在-返回空")
void findByUsername_NotExists_ReturnEmpty() {
Optional<User> result = repo.findByUsername("nonexistent");
assertThat(result).isEmpty();
}
}
参数化测试
@ExtendWith(MockitoExtension.class)
class PriceServiceTest {
@InjectMocks PriceService priceService;
@ParameterizedTest
@MethodSource("discountParams")
@DisplayName("计算折扣-多场景验证")
void calcDiscount_Scenarios(BigDecimal price, int level, BigDecimal expected) {
assertThat(priceService.calcDiscount(price, level))
.isEqualByComparingTo(expected);
}
static Stream<Arguments> discountParams() {
return Stream.of(
Arguments.of(new BigDecimal("100"), 1, new BigDecimal("100")),
Arguments.of(new BigDecimal("100"), 2, new BigDecimal("90")), // 9折
Arguments.of(new BigDecimal("100"), 3, new BigDecimal("80")) // 8折
);
}
}
ArgumentCaptor 参数捕获
@Test
@DisplayName("注册用户-验证发送欢迎邮件")
void registerUser_ShouldSendWelcomeEmail() {
@Captor ArgumentCaptor<EmailMessage> emailCaptor;
given(mailClient.send(any())).willReturn(true);
userService.register("test@test.com", "张三");
then(mailClient).should().send(emailCaptor.capture());
EmailMessage msg = emailCaptor.getValue();
assertThat(msg.getTo()).isEqualTo("test@test.com");
assertThat(msg.getSubject()).contains("欢迎");
}
@Nested 组织测试
@ExtendWith(MockitoExtension.class)
@DisplayName("订单服务测试")
class OrderServiceTest {
@Mock OrderRepository orderRepo;
@InjectMocks OrderService orderService;
@Nested
@DisplayName("创建订单")
class CreateOrder {
@Test
@DisplayName("正常创建-返回订单ID")
void normal_ReturnOrderId() { ... }
@Test
@DisplayName("库存不足-抛异常")
void noStock_ThrowException() { ... }
}
@Nested
@DisplayName("取消订单")
class CancelOrder {
@Test
@DisplayName("已支付-退款并取消")
void paid_RefundAndCancel() { ... }
@Test
@DisplayName("已取消-幂等")
void alreadyCancelled_Idempotent() { ... }
}
}
测试选择决策树
需要测试什么？
├── Service/业务逻辑
│ ├── 纯逻辑(无外部依赖) → @Test + new 对象
│ └── 有DB/HTTP/MQ依赖 → @ExtendWith(MockitoExtension.class) + @Mock/@InjectMocks
├── Controller/API
│ └── @WebMvcTest + @MockBean
├── Repository/数据层
│ └── @DataJpaTest + TestEntityManager
├── JSON序列化
│ └── @JsonTest
└── 集成测试(多组件)
└── @SpringBootTest(慎用，仅关键流程)
Gotchas
- @Mock 不 Mock POJO — 只 Mock 外部依赖，POJO 直接 new
- @SpringBootTest 启动整个上下文(慢) — 优先用切片测试 @WebMvcTest/@DataJpaTest
- AssertJ 断言优于 assertEquals —
assertThat(x).isEqualTo(y)更可读、链式调用 - @MockBean 和 @Mock 不同 — @MockBean 是 Spring 容器中的 Mock(集成测试)，@Mock 是纯 Mockito(单元测试)
- verify() 验证次数默认 times(1) — 调用0次需显式用
never()或times(0) - @MockitoExtension 自动初始化 mocks — 不需要在 @BeforeEach 调用 MockitoAnnotations.openMocks(this)
- 测试方法命名 —
methodName_StateUnderTest_ExpectedBehavior或@DisplayName中文描述 - JUnit5 @Nested 组织相关测试 — 替代 JUnit4 的 @FixMethodOrder
- @InjectMocks 必须是具体类 — 不能是接口或抽象类(需要实例化)
- Mockito 不能 Mock 构造方法、final 类、静态方法(默认) — 需要 PowerMock/Mockito Inline
- BDDMockito.then(mock).should() 替代 verify(mock) — 更符合 Given-When-Then 结构
- @Captor 比手动创建 ArgumentCaptor 更简洁 — 声明式参数捕获
Data Privacy
本技能不收集、存储或传输任何用户数据。
FAQ
What does the junit-mockito-patterns skill do?
JUnit5 + Mockito 测试框架技能。覆盖 JUnit5 @ExtendWith替代@RunWith、Mockito @Mock/@InjectMocks规则、测试隔离原则(FIRST)、@SpringBootTest何时用何时不用(@WebMvcTest/@DataJpaTest切片测试)、BDDMockito given/willReturn风格、ArgumentCaptor参数捕获、verify行为验证、@ParameterizedTest参数化测试。 当用户编写 Java 单元测试/集成测试、Mock外部依赖时需要此技能。
How do I install junit-mockito-patterns?
Run npx skills add https://github.com/full-stack-skills/java-skills --skill junit-mockito-patterns in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/junit-mockito-patterns/ (personal) or .claude/skills/junit-mockito-patterns/ (project).
Which AI agents can use junit-mockito-patterns?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is junit-mockito-patterns safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains junit-mockito-patterns?
It is published by full-stack-skills in full-stack-skills/java-skills. It has 100 recorded installs.
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