单元测试理论PPT，分为四个部分：为什么需要单元测试？怎样征服可测性难题？怎样才能高效率测试？怎样保证测试效果？制作精良，内容精炼。-Unit test theory PPT, divided into four parts: Why unit test? How to conquer the testability problem? How can high-efficiency test? How to ensure test results? Produced, the content o