In this presentation I'd like to share practical experience and techniques that were used for modernization and maintaining 10+ years old legacy system: pitfalls that we've faced during that process and conclusions that we'd made when we've successfully finished updating mission.

1. Testing in Legacy: From Rags to Riches

2. I’d like to share our experience
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3. About me
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“First name”: “Taras”,
“Last name”: “Slipets”,
“E-mail”: “taras.slipets@gmail.com”,
“LinkedIn Profile”: “http://www.linkedin.com/
pub/taras-slipets/
48/466/516”,
“Interests”: [
“Software Engineering”,
“Music”,
“Skiing”,
]
}
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4. About presentation
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5. About presentation
• General feeling about legacy
• System that we’ve received for improvement
• Effective steps that were performed
• What we’ve eventually reached
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6. What does it mean – Legacy system?
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7. Ask expert
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8. Legacy system is…
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9. Just long-term project
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10. Where do we go now
• General feeling about legacy
• System that we’ve received for improvement
• Effective steps that were performed
• What we’ve eventually reached
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11. What we’ve received
• 11-years old system SUCCESSFULLY running on production servers
• Written in Java 1.4
• No frameworks usage
• No documentation
• No developers who has worked on it
• Impatient customers
• Pantient management
• other surprises…
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12. Bus factor
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13. What we’d like to have?
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14. What we’d like to have?
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Shiny system with all cutting-edge frameworks
Reduce pain of maintenance and support

15. What we’d like to have?
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Shiny system with all cutting-edge frameworks
Reduce pain of maintenance and support

16. Where do we go now
• General feeling about legacy
• System that we’ve received for improvement
• Effective steps that were performed
• What we’ve eventually reached
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17. So, how we did it?
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18. Setup your environment
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Let’s deploy
our changes!
Great! Where
do we go?
Directly to production!
“To production!”
he said…

19. Setup your environment
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DEV STAGE PROD

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21. Logs, logs, logs
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22. Domain model – classes level
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23. Domain model – database level
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24. Domain model – workflows
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25. Peer review VERY often
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26. Before changing code
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27. We need to ensure it works
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28. Testing
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29. Testing levels
Unit tests
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Integration testsSystem tests

30. Test existing and expected behavior
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31. System testing (feature testing)
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Application
under testing
System tests
Process Process

32. External world communication
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33. External world communication - mocks
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34. External world communication - mocks
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35. External world communication - mocks
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36. External world communication - mocks
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37. System tests automation
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38. Finally – let’s touch code!
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39. Top occurring issues
• “do-stuff” methods
• “I’m aware of everything” classes
• “Celebrities” classes/interfaces
• “Magic goes here” blocks without comments
• Just obsolete code
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40. What to do?
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41. How about
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42. 42

43. Refactoring facilities
• Extract method
• Extract interface
• Parameter object
• Method object
• Replace type-checking code with
State/Strategy
• Move method/field
• …
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44. Unit tests jumps into
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45. Frameworks
• EasyMock
• Mockito
• PowerMock
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46. Indication
After initial tests are written, use PowerMock as
indicator of bad system design
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47. What is next?
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48. 48

49. 49

50. Most used in our case
• Template method
• Strategy
• State
• Visitor
• Command
• Chain of Responsibility
• Observer
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51. And again - logs, logs, logs
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52. Hey, where are new features?
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53. Extend functionality AFA it’s possible
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54. How deep refactoring should be?
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55. Theory the Godmother
• S.O.L.I.D.
• D.R.Y.
• K.I.S.S.
• …
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56. In real world
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57. Now we can add integration tests
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58. What about build/deployment time?
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59. What about build/deployment time?
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60. Simple rule
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61. But for us it hurt
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62. Remedy?
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63. Remedy
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• Make app self-contained
• Simplify manual installation

64. Operations are happy
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65. If it steal hurts - automate deployment
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66. Where do we go now
• General feeling about legacy
• System that we’ve received for improvement
• Effective steps that were performed
• What we’ve eventually reached
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67. Complete features list + tests for them
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68. The winner takes it all
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69. The dreams come true - build-pipeline!
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70. A-team!
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71. Lessons learned
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72. Lessons learned
• Old project is not a disaster, but challenge
• Start from environment setup and feature testing. At least to
some extent
• Share knowledge with your colleagues and write docs
• Do not underestimate power of classical remedies (patterns,
working techniques)
• Be agile ;)
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73. Links
• http://www.amazon.com/Working-Effectively-Legacy-Michael-
Feathers/dp/0131177052
• http://xpdays.com.ua/archive/xp-days-ukraine-
2011/materials/legacy/
• http://xpdays.com.ua/archive/xp-days-ukraine-
2012/materials/code-story/
• http://jeeconf.com/archive/materials-2014/legacy-projects/
• http://jeeconf.com/materials/web-application-i-have-always-
dreamt-of/
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74. Thanks for your
attention!
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