131-java-testing-unit-testing

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Java Unit testing guidelines

Java单元测试指南

Review and improve Java unit tests using modern JUnit 5, AssertJ, and Mockito best practices.

What is covered in this Skill?

JUnit 5 annotations:

@Test

@BeforeEach

@AfterEach

@DisplayName

@Nested

@ParameterizedTest

AssertJ fluent assertions:
```
assertThat
```
,
```
assertThatThrownBy
```
Given-When-Then test structure, descriptive test naming, single-responsibility tests
Test independence and isolated state
Parameterized tests:
```
@ValueSource
```
/
```
@CsvSource
```
/
```
@MethodSource
```
Mockito dependency mocking:
```
@Mock
```
,
```
@InjectMocks
```
,
```
MockitoExtension
```
Code coverage guidance (JaCoCo), package-private test visibility
Testing anti-patterns: reflection, shared state, hard-coded values, testing implementation details
Error handling:
```
assertThatThrownBy
```
, exception messages
JSpecify null-safety:
```
@NullMarked
```
,
```
@Nullable
```
RIGHT-BICEP coverage principles, A-TRIP test quality, CORRECT boundary condition verification

Scope: The reference is organized by examples (good/bad code patterns) for each core area. Apply recommendations based on applicable examples.

使用现代JUnit 5、AssertJ和Mockito最佳实践来评审和改进Java单元测试。

本Skill涵盖哪些内容？

JUnit 5注解：

@Test

、

@BeforeEach

、

@AfterEach

、

@DisplayName

、

@Nested

、

@ParameterizedTest

AssertJ流畅断言：
```
assertThat
```
、
```
assertThatThrownBy
```
Given-When-Then测试结构、描述性测试命名、单一职责测试
测试独立性与隔离状态
参数化测试：
```
@ValueSource
```
/
```
@CsvSource
```
/
```
@MethodSource
```
Mockito依赖模拟：
```
@Mock
```
、
```
@InjectMocks
```
、
```
MockitoExtension
```
代码覆盖率指导（JaCoCo）、包私有测试可见性
测试反模式：反射、共享状态、硬编码值、测试实现细节
错误处理：
```
assertThatThrownBy
```
、异常消息
JSpecify空安全：
```
@NullMarked
```
、
```
@Nullable
```
RIGHT-BICEP覆盖原则、A-TRIP测试质量、CORRECT边界条件验证

范围：参考文档按每个核心领域的示例（好/坏代码模式）组织。请根据适用示例应用建议。

Constraints

约束条件

Before applying any unit test changes, ensure the project compiles. If compilation fails, stop immediately — do not proceed until resolved. After applying improvements, run full verification.

MANDATORY: Run
```
./mvnw compile
```
or
```
mvn compile
```
before applying any change
SAFETY: If compilation fails, stop immediately and do not proceed — compilation failure is a blocking condition
VERIFY: Run
```
./mvnw clean verify
```
or
```
mvn clean verify
```
after applying improvements
BEFORE APPLYING: Read the reference for detailed examples, good/bad patterns, and constraints

在应用任何单元测试更改之前，确保项目可编译。如果编译失败，请立即停止——在问题解决前不要继续。应用改进后，运行完整验证。

强制要求：在应用任何更改前运行
```
./mvnw compile
```
或
```
mvn compile
```
安全要求：如果编译失败，立即停止且不要继续——编译失败是阻塞条件
验证要求：应用改进后运行
```
./mvnw clean verify
```
或
```
mvn clean verify
```
应用前须知：阅读参考文档以获取详细示例、好/坏模式及约束条件

Reference

参考资料

For detailed guidance, examples, and constraints, see references/131-java-testing-unit-testing.md.

如需详细指导、示例和约束条件，请参阅references/131-java-testing-unit-testing.md