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       做为软件开发工程师一定要懂测试. 你不懂你的全局观还不够. 架构师需要理解测试. 你不懂测试你不会理解测试过程痛, 不能友好的与测试工程师协作. 你不测试说明你的LEVEL还不够高, 对于软件质量理解还不够.  远的测试过程不说, 先说说单元测试UT. 很多开发工程师, 什么高大上微服务项目都做过了, 还是写不好单元测试. 单元测试这是一个普通的技能了. 你写不好, 说明你不专业. 阅读以下内容让我们专业点儿:

      一. 测试的价值

        Tests help us catch mistakes. Tests help us shape our design to actual use.

       注意词Shape,  再者是

Tests help us avoid gold-plating by being explicit about what the required behavior is.

         很多测试因素直接或间接影响 产出效率, 如下图

image

    测试也是个设计工具, 迭代的思想:

 image

    TDD思想出来了, 循环迭代, 有时候与我们做成一件事过程也是相同的.

image

      二. 测试不要依赖真实数据库
        使用内存数据库, 如下的实践

    • Substitute test doubles for third-party library dependencies, wrapping them with your own adapters where necessary. The tricky stuff is then encapsulated inside those adapters that you can test separately from the rest of application logic. 
    • Keep test code and the resources they use together, perhaps in the same package. 
    • Let test code produce the resources it needs rather than keeping them separate from the source code. 
    • Have your tests set up the context they need. Don’t rely on any other tests being run before the one you’re writing. 
    • Use an in-memory database for integration tests that require persistence, as it greatly simplifies the problem of starting tests with a clean data set. Plus, they’re generally superfast to boot up. 
    • Split threaded code into asynchronous and synchronous halves, with all application logic in a regular, synchronous unit of code that you can easily test without complications, leaving the tricky concurrency stuff to a small, dedicated group of tests.

     我们在Test double 概念中也看到 Fake 对象提及 内存数据库

    • Dummy objects are passed around but never actually used. Usually they are just used to fill parameter lists.
    • Fake objects actually have working implementations, but usually take some shortcut which makes them not suitable for production (an InMemoryTestDatabase is a good example).
    • Stubs provide canned answers to calls made during the test, usually not responding at all to anything outside what's programmed in for the test.
    • Spies are stubs that also record some information based on how they were called. One form of this might be an email service that records how many messages it was sent.
    • Mocks are pre-programmed with expectations which form a specification of the calls they are expected to receive. They can throw an exception if they receive a call they don't expect and are checked during verification to ensure they got all the calls they were expecting.

     还有一句有意思话

Friends Don't Let Friends Hit The Database In Tests

     其它BLOG, 还有

Lightweight, drop-in replacement for the database

Aside from substituting a test double for your data access object, the next best thing might be to use a lightweight replacement for your database. For instance, if your persistence layer is built on an ORM framework and you don’t need to hand-craft SQL statements, it likely doesn’t make much of a difference whether the underlying database product is an Oracle, MySQL, or PostgreSQL. In fact, most likely you should be able to swap in something much more lightweight an in-memory, in-process database such as HyperSQL (also known as HSQLDB). The key advantage of an in-memory, in-process database is that such a lightweight alter native conveniently avoids the slowest links in the persistence chain the network calls and the file access.

    

   So far you’ve  learned that unit tests should stay away from the network  interface  and the filesystem if execution speed is a factor. File I/O isn’t exclusive to database.


      Separate Dependencies Where Possible.  尽可能隔离依赖               

                                                                 -- from <<Test-Driving JavaScript Applications >>
      等以上这些都表达不要依赖数据库等外部资源.  笔者在某中型公司框架中还看到误人子弟的单元测试示例,连接了数据库, 那已经不是单元测试, 已变为集成测试.

  三.  Arrange-act-assert 结构

     良好的结构是好的开端

image

        四. 一些原则

         我们原则有 “测试驱动模块化设计”

      “SOLID原则”

image

       代码可测试性原则:

避免复杂private方法
避免final方法
避免static方法
使用new时小心
避免逻辑在构造函数中
避免Singleton
优先组合而不继承
包装外部组件


总结

      理解测试, 是我们需要敏捷软件开发过程基础. 做为一个软件开发工程师你需要比任何一个人都关注质量. 你不能总想着有人帮你测试. 相反是你对你的程序复杂找出BUG修正在正在交给其他人前. 原因很简单, 开发软件总有BUG, 修复BUG是昂贵的. 上升高度, 你的产出影响了其他人, 如何提高你的影响力.



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作者:Petter Liu
出处:http://www.cnblogs.com/wintersun/
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posted on 2019-04-19 23:55 PetterLiu 阅读(...) 评论(...) 编辑 收藏