编写可测试代码

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怎么编写可测试代码?Flaw #1 构造方法做了真实的工作Flaw #2 深入探究辅助对象Flaw #3 脆弱的全局状态和单例Flaw #4 类做了太多事情原文:Guide: Writing Testable Code

怎么编写可测试代码?

Flaw #1 构造方法做了真实的工作

告警标志

在构造方法中的new关键字和字段声明
在构造方法中的static方法调用和字段声明
在构造器中,任何除了字段赋值的工作
在构造方法结束后,对象仍然没没有完全初始化
在构造器中的分支逻辑(if,loop)
在构造器内完成了复杂的对象图构造而不是使用工厂方法.
添加或者使用初始化block

Flaw #2 深入探究辅助对象

告警标志

对象传递进来,却从未直接使用(只是间接使用了其他对象)
对象的方法调用使用了链式的调用(a.b.c之类的)
可疑的命名:例如

context

,

environment

,

principal

,

container

,or

manager

Flaw #3 脆弱的全局状态和单例

告警标志

添加和使用单例
添加和使用静态属性和静态方法
添加和使用静态的初始化block
添加和使用registries(什么东西?)
添加是使用service locators(什么东西?)

Flaw #4 类做了太多事情

告警标志

使用了and来总结这个类做了什么
类对与新人快速熟手有很大的挑战
类有一些只有在某些方法使用的字段
类有只操作了一个参数的静态方法

原文链接:http://misko.hevery.com/code-reviewers-guide/

原文:Guide: Writing Testable Code

To keep our code at Google in the best possible shape we provided our software engineers with these constant reminders. Now, we are happy to share them with the world.

Many thanks to these folks for inspiration and hours of hard work getting this guide done:

Jonathan Wolter
Russ Ruffer
Miško Hevery
Also thanks to Blaine R Southam who has turned it into a pdf book.

Flaw #1: Constructor does Real Work

Warning Signs

new keyword in a constructor or at field declaration
Static method calls in a constructor or at field declaration
Anything more than field assignment in constructors
Object not fully initialized after the constructor finishes (watch out forinitialize methods)
Control flow (conditional or looping logic) in a constructor
Code does complex object graph construction inside a constructor rather than using a factory or builder
Adding or using an initialization block
Flaw #2: Digging into Collaborators

Warning Signs

Objects are passed in but never used directly (only used to get access to other objects)
Law of Demeter violation: method call chain walks an object graph with more than one dot (.)
Suspicious names: context, environment, principal, container, or manager
Flaw #3: Brittle Global State & Singletons

Warning Signs

Adding or using singletons
Adding or using static fields or static methods
Adding or using static initialization blocks
Adding or using registries
Adding or using service locators
Flaw #4: Class Does Too Much

Warning Signs

Summing up what the class does includes the word “and”
Class would be challenging for new team members to read and quickly “get it”
Class has fields that are only used in some methods
Class has static methods that only operate on parameters