Changing code in a professional way make life easier

This presentation is talking about how to make code change safely

Transcript

1. Changing code In professional way make life easier By Liang
2. Table of contents Changing software • Four Reasons to Change Software • Risky change 2
3. Changing software Four Reasons to Change Software • Adding a feature • Fixing a bug • Improving the design • Optimizing resource usage 3
4. Changing software Putting It all together Adding a Feature Fixing a Bug Refactoring Optimizing Structure Changes Changes Changes - New Functionality Changes - - - Functionality - Changes - - Resource usage - - - Changes 4
5. Changing software Putting It all together all at risk ? Existing Behavior New Behavior 5
6. Risky Change To mitigate risk, we have to ask three questions: 1. What changes do we have to make? 2. How will we know that we’ve done them correctly? 3. How will we know that we haven’t broken anything? 6
7. Risky Change Changing with care is not silver bullet Don’t Change The Code I’ll Kill you ! 7
9. 9 I am only human I make mistakes
10. Risky Change Preserving behavior is a large challenge. Teams tend to void change. Don’t Change The Code! 10
11. Risky Change Developers might tend to • Copy code • Only add some lines of code for specific condition • Add new method and rewrite same logic I’ll Kill you ! 11
12. Consequence of avoiding change • Get rusty at it • Become monster class, methods 12
13. Consequence of avoiding change • Incredible fear of change get worse every day. 13
14. Good Project Calm down I’ll Kill you ! Bad Project Feary 14
15. Alternative ? 15
16. Software changes can be made in two primary ways • Edit and Pray • Cover and modify 16
17. Safety net of Unit tests 17
18. The day-to-day goal in legacy code is to make changes, but not just any changes. We want to make functional changes that deliver value while bringing more of the system under test. At the end of each programming episode, we should be able to point not only to code that provides some new feature, but also its tests. Over time, tested areas of the code base surface like islands rising out of the ocean. Work in these islands becomes much easier. Over time, the islands become large landmasses. Eventually, you’ll be able to work in continents of test-covered code. - Michael C. Feathers (Author of Working Effectively with Legacy Code) 18
19. HOW ? 19
20. Next ? Working with feedback • What is Unit Testing • High-Level Testing • Test Coverings • The Legacy Code Change Algorithm 20
21. Summary • For changing code there are ways make life difficult or much easier. • Changing code could involves behavioral change(functional change). • Four reasons to change software. • To make it safe people change with care, but not a silver bullet. • Teams tend to avoid change due to fear. • Changing on good project usually make developer confident. • How to make life easier ? pind down the behavior with unite test. 21