按照定义，不能从密封类型继承，意味着不能调用密封类型上受保护的方法。

By definition, you cannot inherit from a sealed type, which means that protected methods on sealed types cannot be called.

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这种方法使得测试受保护的方法非常容易，因为测试案例类现在可以扩展包含受保护方法的类了。

This approach makes testing protected methods much easier because the test case class can now extend the class that contains the protected methods.

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为了提供一致的开发人员体验，公共公开的元素(如公共类和受保护的方法)必须遵守这些准则。

To provide a consistent developer experience, these guidelines are required for publicly exposed elements such as public classes and protected methods.

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