Stanly Lau is an agile coach and software developer based in Singapore who has worked with companies of various sizes in industries such as insurance, mobile safety, education, logistics, and banking. The document discusses legacy code and provides tips on how to deal with it. Legacy code is defined as code without unit tests that is difficult to change and prone to bugs. It recommends adopting modern engineering practices like test-driven development and refactoring. It also outlines an approach for identifying change points, breaking dependencies, writing tests, and then making changes to legacy code in a safe manner.

1. www.odd-e.com
Fight Legacy Code!
Write Unit Test!
Stanly Lau

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I’m Stanly
• Lives in Singapore!
• Agile coach, SW developer!
• Worked in small to large
companies!
• Experienced in Insurance, Mobile
Safety, Education, Logistics and
Banking!
• Java, .Net, JavaScript, Objective-C
stanly@odd-e.com

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What is Legacy Code?!
!
The Problem!
!
How to deal with it?

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7. What is legacy code?
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8. Legacy Code is!
Code without Unit Test
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Michael Feathers

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It is not a unit test when:
• It talks to the database!
• It communicates across the network!
• It touches the file system!
• It can't run at the same time
as any of your other unit tests!
• You have to do special things to your
environment (such as editing config
files) to run it.
Michael Feathers

10. The problem
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Inheritance nightmare

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Code tends to grow

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amount of bad
code
panic
amount of code
smells
time spend on
bug fixing
motivation
developers
quick hacks
opportunity for
# of bugs
indicates
O
refactoring
O

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Existing Behaviour New
This is where we spent most time on,!
preserving behaviour!
Codebase

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Productive
Working duration in a day
Does your day
looks like this?

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Productive =(
Don’t know why the ‘if’
doesn’t work

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Productive =(
Stuck on
understanding what the
code is doing

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Productive =(
Stuck on thinking of a
general solution to solve multiple
problems

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Productive =(
Realised you misunderstood
the requirements

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Productive
=(
Fixing production bug

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Features
Estimates
Business Developers
Competitive dynamic
Limits everyone’s
perspectives

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James Grenning
“Software change is part of being a
developer, so you better get used to it. !
Even more, you better get good at it!”

23. How to deal with it?
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Modern engineering practices
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Test-Driven
Development
Refactoring
Continuous
Integration
Emergent Design

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Test-driven development
•Increments of functionality!
•Always in working state
Code and fix
•Large functionalities!
•Long time to get to a working statef
t

26. The Legacy Code Dilemma
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When we change code, we should have tests in place. To put tests in
place, we often have to change code.

27. But I don't understand the code
well enough to change It =(
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Scratch Refactoring
Notes/Sketching
Delete Unused Code

28. Legacy code algorithm
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1. Identify change point!
2. Find test points!
3. Break dependencies!
4. Write tests!
5. Make changes and refactor

29. Exercise:!
Dependency Breaking!
Characterisation Tests!
!
http://bit.ly/FightLegacyCode
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30. Are we going faster?
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Feels faster
Feels slower

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Kent Beck
“I'm not a great programmer;!
I'm just a good programmer with great
habits”

32. Closing
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33. Books - Technical Practices
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@avernois

35. stanly@odd-e.com
!
@stanlylau
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