可扩展且可用于单个地或以多个单元为单位测试程序代码的层次结构。

Extensible and can be used to test a hierarchy of program code either singularly or as multiple units.

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把测试案例和被测试的程序代码放在同一个单元里面。

Placing test cases in the same unit as the tested code.

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在后来到了更新或升级继承来的应用程序代码的时候，这些测试案例也是有帮助的。

These test cases will also be helpful later on when the time comes to update or upgrade the inherited application code.

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Having reached the end of the block, go back up and check the test.

执行到了这块代码的最后，程序会回去再做一次测试。

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