# 扩展配置异常：扩展 [com.example.MyExtension] 未注册

- **ID:** `java/junit-extension-not-registered`
- **领域:** java
- **类别:** config_error
- **验证级别:** ai_generated
- **修复率:** 80%

## 根因

通过 @ExtendWith 使用自定义 JUnit 扩展，但未正确注册或类未找到。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| 8+ | active | — | — |

## 解决方案

1. **Register extension with @RegisterExtension** (90% 成功率)
   ```
   @RegisterExtension
static MyExtension extension = new MyExtension();
   ```
2. **Ensure extension class is public and has no-arg constructor** (85% 成功率)
   ```
   public class MyExtension implements BeforeEachCallback {
    public MyExtension() { }
}
   ```

## 无效尝试

- **Removing @ExtendWith annotation** — Extension functionality is lost; tests may fail. (60% 失败率)
- **Adding extension as a dependency in build file** — Extension is already available; registration issue is different. (40% 失败率)