Legacy code is something we all deal with. How can you figure out where to start untangling the big ball of mud you've been handed. Note: photos excluded from CC LIcense.

1. THEY CALL IT LEGACY
Because it's killing me to work on it
Tuesday, July 9, 13

2. WHERE DO I START?
Tuesday, July 9, 13

3. WHO AM I?
• Twitter: @arlen
• GitHub: Paladin
• Blog: http://www.theodicius.com
• Coderwall: https://coderwall.com/paladin
• MojoLive: http://mojolive.com/profile/paladin
• LinkedIn: www.linkedin.com/in/arlenwalker/
Tuesday, July 9, 13

4. LEGACY CODE
It's everywhere
Tuesday, July 9, 13

5. IT WASTHERE BEFORE
YOU ARRIVED
It'll be there after you're gone
Tuesday, July 9, 13

6. YOU DON'T
UNDERSTAND IT
Will those who follow you understand yours?
Tuesday, July 9, 13

7. YOU DON'T KNOWTHEIR
SKILL OR KNOWLEDGE
How will those who follow you know yours?
Tuesday, July 9, 13

8. THETRUTH IS INTHE
CODE
Yes,Agent Mulder. But where?
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9. Tuesday, July 9, 13

10. NOWTHATYOU HAVE IT
What are you going to do with it?
Tuesday, July 9, 13

11. REWRITE IT?
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12. Tuesday, July 9, 13

13. WATCH ME REWRITETHAT
CODE FROM SCRATCH!
That trick never works!
Tuesday, July 9, 13

14. WHAT’STHE PAIN POINT?
Why are you here in the first place?
Tuesday, July 9, 13

15. THETARRASCH PRINCIPLE
“When there is nothing
concrete to do, improve the
position of your worst
piece.”
Tuesday, July 9, 13

16. OK, SIGGY OLD BOY
How do I measure my
“worst piece” of software?
Tuesday, July 9, 13

17. W. EDWARDS DEMING
"You can't manage what
you can't measure"
Tuesday, July 9, 13

18. STOP AND SMELLTHE
CODE
Code “smells” are simple metrics you can use to
quickly locate potential trouble spots
Tuesday, July 9, 13

19. ODOR - STATIC CALL
Class::method() syntax reduces the code’s flexibility
Tuesday, July 9, 13

20. ODOR - LONG
ARGUMENT LIST
Many arguments may mean the method is connected
to the code in too many ways.
Tuesday, July 9, 13

21. ODOR - LONG METHOD
Too many lines may mean the method is trying to do
too much
Tuesday, July 9, 13

22. ODOR - LARGE CLASS
A class with too many methods may be trying to do
too much
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23. MORE COMPLEX CODE
METRICS
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24. NPATH COMPLEXITY
Number of paths through the code
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25. ACYCYLIC
DEPENDENCIES
Classes that depend upon classes that depend upon
them
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26. CYCLOMATIC
COMPLEXITY
Paths - nodes + 2 * endpoints
Tuesday, July 9, 13

27. CHANGE RISK ANALYSIS
AND PREDICTION
CC(m)^2 * (1 – Coverage(m)/100)^3 + CC(m)
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28. ARETHERETESTS?
Don't be silly
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29. YOU NEEDTESTS
Tests need seams
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30. DEBUGGINGTHROUGHTESTINGTHE COMPLETE
CODE STACK
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31. Find an existing seam, if possible
Create new seams by sprouting a new class or
method
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32. NOWYOU HAVETESTS
Are we there yet?
Tuesday, July 9, 13

33. HOW DO I USETHE
METRICS?
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34. SIMPLICATE
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35. TOO MANY METHODS?
Look to move some methods into new objects
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36. METHODTOO LONG?
Extract smaller methods from it.
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37. OBJECTTOO COMPLEX?
Simplify the coding by enforcing command/query
separation
Tuesday, July 9, 13

38. TOOLS!
You said there would be tools!
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39. DANGER,WILL ROBINSON!!
Don’t confuse the map with
the territory.The metrics are
a map to the location of
possible problems in your
code.They are not your
code.
Use the metrics, don’t let the
metrics use you.
Publicity photo from “Lost in Space”
Tuesday, July 9, 13

40. COPY/PASTE DETECTION
Finds code duplication in your project. Extracting them into a
single method will make future maintenance easier It will also
shorten the methods including them.
Identical methods across multiple classes make good
candidates for inheritance orTraits.
https://github.com/sebastianbergmann/phpcpd
Tuesday, July 9, 13

41. PHPUNIT
The most popular automated unit testing framework for php,
used in most significant open source projects, such as Drupal,
Joomla, Zend Framework2, Symfony2, etc.
Calculates a CRAP index on the code as part of the coverage
report, but only for code executed as part of running the tests.
Manual: http://phpunit.de/manual/current/en/index.html (also
available in ePub and PDF files)
Code: https://github.com/sebastianbergmann/phpunit/
Tuesday, July 9, 13

42. PHP MESS DETECTOR
The PHP Project Mess Detector goes through single files or an
entire project looking for many potential problem areas. It has
some factors included in it, but you can create your own tests,
if you have others you’d like to rely on.
http://phpmd.org
Tuesday, July 9, 13

43. PHP DEPEND
PHP Depend is a small program that generates several
different reports about the condition of a code project it’s
pointed at.Aside from the “normal” reports, it produces two
graphics that are quite useful for giving you a general idea of
what you’re looking at: the Abstraction-Instability Chart and
the Overview Pyramid.
Code & Docs: http://www.pdepend.org/
Tuesday, July 9, 13

44. THE OVERVIEW PYRAMID
This is a high-level view of the metrics of the system. It
calculates the cyclomatic complexity, counts lines of code,
methods, classes and packages. It also counts the distinct
method calls, and “fan-out,” the references from a class to a
class in a different inheritance branch, and analyses the
inheritance heirarchy.
Tuesday, July 9, 13

45. OVERVIEW PYRAMID CHART
The overview Pyramid
charts for Drupal,Wordpress
and Joomla give us a “50,000
ft” view of the systems.
Tuesday, July 9, 13

46. ABSTRACTION AND
INSTABILITY
The Abstraction metric (0-1) is measure of how easily the
system can be expanded/modified.
The instability metric (0 - 1) is an attempt to measure the ease
of change.
Packages approaching [0,0] are rigid. Packages approaching [1,1]
are completely abstract, therefore useless.The “happy meridian”
is a diagonal through the center of the chart.
http://www.objectmentor.com/resources/articles/oodmetrc.pdf
Tuesday, July 9, 13

47. ABSTRACTION-INSTABILITY
CHART
These are the A-I charts for
Drupal,Wordpress, and Joomla.
Drupal has very few objects
but they’re well balanced.
Wordpress has more, but no
abstraction.
Joomla has a wide range of
objects, not all well-balanced.
Tuesday, July 9, 13

48. SYMFONY2
Here are the charts for the
Symfony2 framework.
The overview looks very
good, while the A-I chart
shows a well-distributed mix
of objects in the system.
Tuesday, July 9, 13