junit-5-skill

JUnit 5 测试技能

你是一名专注于 JUnit 5 测试的资深 Java 开发者。

步骤 1 — 测试类型

├─ "unit test", "assert" → Standard unit test
├─ "parameterized", "multiple inputs" → @ParameterizedTest
├─ "mock", "Mockito" → Unit test with Mockito
├─ "integration test", "Spring" → Read reference/spring-integration.md
└─ Default → Standard unit test

核心模式

基本测试

import org.junit.jupiter.api.*;
import static org.junit.jupiter.api.Assertions.*;

class CalculatorTest {
    private Calculator calculator;

    @BeforeEach
    void setUp() {
        calculator = new Calculator();
    }

    @Test
    @DisplayName("Addition of two positive numbers")
    void addPositiveNumbers() {
        assertEquals(5, calculator.add(2, 3));
    }

    @Test
    void divideByZero_throwsException() {
        assertThrows(ArithmeticException.class, () -> calculator.divide(10, 0));
    }

    @Test
    void multipleAssertions() {
        assertAll("calculator operations",
            () -> assertEquals(4, calculator.add(2, 2)),
            () -> assertEquals(0, calculator.subtract(2, 2)),
            () -> assertEquals(6, calculator.multiply(2, 3))
        );
    }
}

断言参考

assertEquals(expected, actual);
assertNotEquals(unexpected, actual);
assertTrue(condition);
assertFalse(condition);
assertNull(object);
assertNotNull(object);
assertThrows(IllegalArgumentException.class, () -> service.process(null));
assertTimeout(Duration.ofSeconds(2), () -> service.longRunningOp());
assertAll("group",
    () -> assertNotNull(user.getName()),
    () -> assertTrue(user.getAge() > 0)
);
assertIterableEquals(List.of(1, 2, 3), actualList);

参数化测试

@ParameterizedTest
@ValueSource(strings = {"hello", "world", "junit"})
void stringIsNotEmpty(String value) {
    assertFalse(value.isEmpty());
}

@ParameterizedTest
@CsvSource({"1,1,2", "2,3,5", "10,-5,5"})
void addNumbers(int a, int b, int expected) {
    assertEquals(expected, calculator.add(a, b));
}

@ParameterizedTest
@MethodSource("provideUsers")
void validateUser(String name, int age, boolean expected) {
    assertEquals(expected, validator.isValid(name, age));
}

static Stream<Arguments> provideUsers() {
    return Stream.of(
        Arguments.of("Alice", 25, true),
        Arguments.of("", 25, false),
        Arguments.of("Bob", -1, false)
    );
}

@ParameterizedTest
@NullAndEmptySource
@ValueSource(strings = {"  ", "\t"})
void blankStringsAreInvalid(String input) {
    assertFalse(validator.isValid(input));
}

使用 Mockito 进行模拟

@ExtendWith(MockitoExtension.class)
class UserServiceTest {
    @Mock private UserRepository userRepo;
    @Mock private EmailService emailService;
    @InjectMocks private UserService userService;

    @Test
    void createUser_savesAndSendsEmail() {
        User user = new User("[email protected]", "Alice");
        when(userRepo.save(any(User.class))).thenReturn(user);

        User result = userService.createUser("[email protected]", "Alice");

        assertNotNull(result);
        verify(userRepo).save(any(User.class));
        verify(emailService).sendWelcomeEmail("[email protected]");
    }

    @Test
    void getUser_notFound_throwsException() {
        when(userRepo.findById(99L)).thenReturn(Optional.empty());
        assertThrows(UserNotFoundException.class, () -> userService.getUser(99L));
    }
}

嵌套测试

@DisplayName("UserService")
class UserServiceTest {
    @Nested
    @DisplayName("when creating a user")
    class CreateUser {
        @Test void withValidData_succeeds() { }
        @Test void withDuplicateEmail_throwsException() { }
    }

    @Nested
    @DisplayName("when deleting a user")
    class DeleteUser {
        @Test void existingUser_removesFromDb() { }
        @Test void nonExistentUser_throwsException() { }
    }
}

反模式

不推荐	推荐	原因
@Test public void test1()	@Test void shouldCalculateSum()	名称具有描述性
测试私有方法	通过公共 API 测试	实现细节
不使用 @DisplayName	始终添加显示名称	报告更清晰
assertEquals(true, x)	assertTrue(x)	可读性更好

Maven 依赖项

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter</artifactId>
    <version>5.11.0</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-junit-jupiter</artifactId>
    <version>5.14.0</version>
    <scope>test</scope>
</dependency>

快速参考

任务	命令
运行全部测试	mvn test 或 ./gradlew test
运行测试类	mvn test -Dtest=UserServiceTest
运行测试方法	mvn test -Dtest=UserServiceTest#createUser_succeeds
运行带标签的测试	@Tag("slow") + mvn test -Dgroups="slow"
禁用	@Disabled("Reason")
条件执行	@EnabledOnOs(OS.LINUX)
超时	@Timeout(value = 5, unit = TimeUnit.SECONDS)
重复执行	@RepeatedTest(5)
排序	@TestMethodOrder(MethodOrderer.OrderAnnotation.class)

深入模式

生产级模式请参阅 reference/playbook.md：

章节	内容
§1 项目设置	Maven 依赖项、并行配置、surefire
§2 测试生命周期	BeforeAll/Each、排序、标签
§3 参数化	CsvSource、MethodSource、EnumSource、ValueSource
§4 Mockito	@Mock/@InjectMocks、捕获器、验证顺序
§5 嵌套与动态测试	@Nested 分组、@TestFactory
§6 AssertJ	流式断言、提取、集合检查
§7 条件执行	@EnabledOnOs、假设、@EnabledIf
§8 自定义扩展	计时、重试、BeforeTestExecution
§9 CI/CD	使用测试报告器的 GitHub Actions
§10 调试表	8 个常见问题及其解决方法
§11 最佳实践	12 项生产检查清单