Entering the matrix
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This document discusses strategies for working with legacy code. It defines legacy code as code that is difficult to change and inherited from previous developers. It recommends first understanding the code by finding known keywords and tracing actions backwards. Then cover the code with 100% test coverage, starting with the shortest code branches. Next refactor the code, starting with the deepest code branches. Finally, when adding new features, add tests first and keep new code separate to avoid issues testing both old and new code together. The document emphasizes testing unknown code, extracting code sections, and splitting screens and using shortcuts to work efficiently.
![EXAMPLE: Subclass and Override
public class A {
public void do1(…) {
user = session.getAttribute(“user”);
...
}
}
Souce Code
public void do1(…) {
...
logged = isLogged(“mario")
}
protected Boolean isLogged(..)
public class ATest
{
[TestMEthod]
public void do1WhenLogged() { }
private class TestableA : A
{
protected override boolean isLogged()
{
return true
}
}
}
Test Code](https://image.slidesharecdn.com/workshop-enteringthematrix-170904150507/85/Entering-the-matrix-18-320.jpg)
Entering the matrix
- 1. ENTERING THE MATRIX Work with Legacy Code F. Garavaglia 08/2017 v. 1.0
- 2. o Photographer o High-Aggressive-I-eat-you- German-Shepherd- Protected-by I’m Francesco Garavaglia o over 10 years of experience in IT consulting companies. o Took part in large scale projects (Energy Markets, Bank, Insurance) o Pay attention to Software architecture and Business value
- 3. Agenda ◦ What is “Legacy Code”? ◦ See how it’s deep the white rabbit’s hole ◦ Code Samples
- 4. WHAT’S “LEGACY CODE”? What problems are we trying to solve? 1
- 5. What’s “Legacy Code”? Quiz: Legacy Code? A. Code difficult to change B. Inherited code difficult to change C. Valuable code we’re afraid to change
- 6. What’s “Legacy Code”? Is there a Pragmatic Approach? Should I care about it? What about your feelings?
- 8. What’s “Legacy Code”? o Nervous (I depend on… ) “engaged” with debugger , complex infrastructure o Fear / Under pressure .. so I do changes inside the existing code o Unsafe Did i broke something ? Is this working ? o Resigned “Edit and pray”
- 9. What’s “Legacy Code”? o My Diagnosis: You are in Matrix: Then, you have to take a pill
- 11. THE WHITE RABBIT’S HOLE See how it is deep and dark 2
- 12. The white rabbit’s hole We need a map for this journey: how can we face with Legacy code? UNDERSTAND COVER REFACTOR CHANGE Each step has different target: focus on 1 at times.
- 13. The white rabbit’s hole: HOW • Use it before looking at the code • Find one thing you know 1. look for keywords 2. and trace the actions backward • Sketch refactoring • Keep reading someone else code
- 14. The white rabbit’s hole: COVER You need 100% of test coverage if condition1 …. …. if condition2 ….. ….. if condition3 ….. ….. else ….. ….. else ….. ….. else ….. ….. Start from shortest to deepest branch
- 15. COVER: test the unknown assume to know what the code is supposed to do … but what if we don’t ? •Test name ??? •Expected result ???
- 16. COVER: test the unknown 1. Write a test named “x” 2. Set any expected result 3. Run it and get a Failure 4. Copy the text and make it pass 5. Give a better name
- 17. COVER: test the unknown Extract the code you want to change in a separate section - Smaller problem to solve - Quicker way to the coverage
- 18. EXAMPLE: Subclass and Override public class A { public void do1(…) { user = session.getAttribute(“user”); ... } } Souce Code public void do1(…) { ... logged = isLogged(“mario") } protected Boolean isLogged(..) public class ATest { [TestMEthod] public void do1WhenLogged() { } private class TestableA : A { protected override boolean isLogged() { return true } } } Test Code
- 19. The white rabbit’s hole: REFACTOR • Related to change phase Start End Add a Test Hard to Create or Make it Pass? Refactor Apply the change
- 20. The white rabbit’s hole: REFACTOR • Start from the deepest brach if condition1 …. …. if condition2 ….. ….. if condition3 ….. ….. else ….. ….. else ….. ….. else ….. …..
- 21. The white rabbit’s hole: CHANGE Adding a new feature: Common mistake “Let’s put new feature inside this existing method because it should happen at the same time” Problem : … test old and new code together
- 22. EXAMPLE: Adding a new feature public void do1() { … // new Feature(..).apply(…) } Souce Code public class Feature { public void apply(…) { … } } public void do1() { … new Feature(..).apply(…) } Productive Code TDD
- 23. DON’T REPEAT YOURSELF ◦ Split screen vertically TDD ◦ Continuous testing plugin ◦ Use shortcuts instead of repeating actions ◦ Small commits / steps
- 24. Thanks Thank you for your time Francesco.garavaglia@gmail.com
- 25. REFERENCES • Refactoring: Improving the Design of Existing Code https://www.amazon.it/Refactoring-Improving-Design-Existing- Code/dp/0201485672/ref=sr_1_1?ie=UTF8&qid=1504536816&sr=8- 1&keywords=Refactoring%3A+Improving+the+Design+of+Existing+Code • M. Feathers- Working Effectively with Legacy Code https://www.amazon.it/Working-Effectively-Legacy-Michael- Feathers/dp/0131177052/ref=sr_1_1?s=english-books&ie=UTF8&qid=1504536861&sr=1- 1&keywords=Working+Effectively+with+Legacy+Code%3A+Michael+Feathers