What is a use case?

A use case is a description of the ways in which a user interacts with a system or product. A use case may establish the success scenarios, the failure scenarios, and any critical variation or exceptions.

描述用户和系统和产品的交互行为。，可以建立成功的，失败的场景，还有一些异常的场景。

                What is the purpose of a QA engineer in a software development team?

As we know, people make mistakes. people design and build the software and they can make mistakes during the design and build. when the software code has been built, it is executed and then any defects may cause the system to fail to do what it should do. The QA is necessary during development and maintenance to identify defects, in order to reduce failures in the operational environment and increase the quality of the operational system.

我们知道是人就会犯错，当开发团队去设计和开发一个软件的时候很有可能会产生错误。当代码被写入，被执行就会产生让系统失败的错误。QA 必须在开发和维护的时候去识别错误目的是为了降低运营环境的失败和增加运营系统的质量。