Question

Part1 The Mechanics of Change

1.Changing Software

Four primary ressons: 1. Adding a feature 2. Fixing a bug. 3. Improving the design 4. Optmmizing resoource usage

structure, functionality, resource usage

ask three questions: 1. What chagnes do we have to make? 2. How will we know that we've doen them correctly? 3. How will we know that we have't broken anything?

2. Working with Feedback

Changes in a system 2 ways: Edit and Pray: Cover and Modify: tests

The legacy code change algorith: 1. Identify change points. 2. Find test points. 3. Break dependencies. 4. Write tests. 5. Make changes and refactor.

3. Sensing and Sepatation

fake objects mock objects

4.The Seam Model

5. Tools

Mock Objects Unit-Tesiting Harnesses

Part2 The Mechanics of Change

6. Don't Have Much Time and I Have to Change It

Sprout method

7. It Takes Forever to make a change

减少依赖

8. How Do I Add a Feature?

TDD: Programming by Difference

9. I Can't get this class into a test Harness

恼人的参数：如果构造函数的参数依赖其他对象， 可以通过构造fake对象作为参数传入，通过继承原对象并用空方法复写父类。 隐藏的依赖：不要在函数里隐藏依赖， 最好用函数参数的形式传入。 如果隐藏依赖过多，穿参数会导致大量参数，可以使用方法替换掉内部的实例变量。setter方法 全局依赖：对于单例模式等class，可以使用静态setter函数

11.I need to Make a Change, WHat methods should I test?

找到会受影响的代码

12.I need to make many changes in one Area. Do I have to break dependices for all the classes involved.

Interception Points: 由变更点决定。 把Interception point作为封装的边界

13. I need to make a change, but i don't know what tests to write.

Characterization test.

14. Dependencies on Libraies are killing me.

15. My application is all api callls

Responsibiliy-based extraction

16.I don't understand the code well enough to change it

Notes(Sketching): 通过画图和做笔记的形式理解代码，画出之间的连接和关系。 Lising Markup: Separating Responsibilities; Understanding Method Structure; Extract Methods; Understand the Errects of a change. Scratch Refacting: Deleted Unused code

17. My Application Has no structure

Telling the Story of the system: 互相解说 Naked CRC: Class, Responsiblity and Collaborations. 1. Cards represent instances, not clases. 2. Overlap cards to show a collection of them Conversation srutiny:

18. My Test Code is in the way

Class Naming Conventions: 对于测试类和Fake类通过后缀或者前缀来区别。 Test Location:

19. My Project is not Object Oriented. How do I make changes ?

通过预处理器宏添加测试 Adding New Behavior:

20. This class is Too big and I don't want it to get any bigger

不要写过大（方法太多）的类，会导致混淆、 Single-Responsibility Principle(SRP): It should have a single purpose in the system, and there should be only one reason to change it 。如何确定职责？功能相近的应该有类似后缀，根据功能划分。() Seeing Responsibilities: - 1. Group Methods(写出所有方法名和访问权限) - 2. Look at Hidden Methods - 3. Look for Deciions that can change. - 4. Look for internal relationships（写出所有变量和方法使用的变量，画出调用关系，根据把调用关系分成的几个大区域来拆分class）. - 5. Look for the primary responsibility.(尝试使用一句话描述类的职责) 接口隔离原则 - 6. When all else fails, do some scratch refactoring - 7. Focus on the current work.

21. I'm Changing the same code all over the place

开闭原则

22. I need to change a Monster method and I can't wirte tests for it

Varieties of Monster: Bullete Methods(没有缩进); Snarled methods(单一大块代码段); Tackling Monsters with automated refactoring support: - To separate logic from awkward dependencies - To introduce seams that make it easier to get tests in place for more refactoring

The manual refactoring challenge:

22. How Do I know That I'm Not Breaking Anything?

Hyperaware Editing Single-Goal Editing: doing one thing at a time Proserve Signatures Lean on the Compiler Pair Programming

24. We Feel Overwhelmed, It Isn't going to Get any better.

Finding what motivates you 如果因为代码质量团队士气低：找到最丑的代码类，然后让测试覆盖它。

25. Dependency-Breaking Techniques