Taming the Monster Legacy Code Beast
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Does that legacy code beast stifle your creativity? Do you stay up late at night frightened that someone might touch *that* piece of code? Learn some practical steps on how you can slay the legacy code beasts, divide and conquer, and deliver value to your customers.
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Taming the Monster Legacy Code Beast
- 1. Taming Legacy Code Monsters
- 2. *Caleb* I’m here to help.
- 4. Last year10Reasons yoursoftwareSucks(and the 10 practicesto fix it)
- 5. Building teams that engineer better softwareDevelopment ∙ Team Work ∙ Process
- 6. back to…Taming Legacy Code Monsters
- 7. back to…Taming Legacy Code Monsters
- 8. Definition “Legacy”n. Software that I’m afraid to maintain, extend, or change it actually scares me to touch that code.
- 9. What’s the differencebetween an application and
- 10. Legacy Monster
- 11. Legacy MonsterProcessorStatic ConfigStatic ProxyProcessor SettingsData ConnectionsRules ConfigurationsCouplingCouplingCouplingCouplingCouplingRulesDataCoupling
- 12. Legacy MonsterSolution contained over 68 projects.Most of which were notused.No horizontal layers.Required IIS 6 / legacy URL rewriter / 32 bit C Lib / IIS Rules export/import / Database Connections / Proper Configuration X 3To run or test ANY part on a dev box…
- 13. Strategy #1Know your Foe
- 15. Strategy #1Visual Studio Dependency Graph
- 16. Strategy #1DemoUsing theVisual Studio Dependency Graph
- 17. Strategy #1DemoPro tip:Look for big blobs& thick linesto concrete types
- 18. Strategy #2Create aSafety Net
- 19. Source Control+ TestStrategy #2
- 20. Strategy #2Source Control+ Test
- 22. // source// svn / git / tfs .. // r1.1// r1// r2// r3// trunk// trunkBranching for FUN!//
- 23. Strategy #2Unit TestsIntegrationRegressionLoad TestsEtc…Tests
- 24. Isolation and White box Unit Testing for .NETDemo: Safety NetLegacy Monster“Pexautomatically generates test suites with high code coverage.…[and] finds interesting input-output values of your methods, which you can save as a small test suite with high code coverage. Microsoft Pex is a Visual Studio add-in for testing .NET Framework applications.”ProcessorStatic ConfigStatic IProxyProcessor SettingsData ConnectionsRules Configurationshttp://research.microsoft.com/en-us/projects/pex/RulesData
- 25. what about hard to test code?refactoring testability
- 26. privateIList<Bean> goodBeans { get; set;}privateIList<Bean> badBeans { get; set;}publicvoidAddBean(Bean bean){ if(bean.size > 10)goodBeans.Add(bean); elsebadBeans.Add(bean);}publicvoidUpdateBeans(){BeanData.Update(goodBeans);goodBeans.Clear();badBeans.Clear();}
- 27. 1Clearly an arbitrary exampleDoes represent actual production code that I have worked with23AddBean(b); AddBean(b), UpdateBeans();Usage scenario isHow can we test the AddBean() Logic?
- 28. publicIList<Bean> GoodBeans{ get; private set;}privateIlist <Bean>badBeans{ get; set;}publicvoidAddBean(Bean bean){if(bean.size > 10)GoodBeans.Add(bean);elsebadBeans.Add(bean);}publicvoidUpdateBeans(){BeanData.Update(goodBeans);GoodBeans.Clear();badBeans.Clear();}privateIList<Bean> goodBeans { get; set;}privateIList<Bean> badBeans { get; set;}publicvoidAddBean(Bean bean){ if(bean.size > 10)goodBeans.Add(bean); elsebadBeans.Add(bean);}publicvoidUpdateBeans(){BeanData.Update(goodBeans);goodBeans.Clear();badBeans.Clear();}A: create a readonlyaccessor to “sense” thegoodBean state externally
- 29. What about the UpdateBeans() method?publicvoidUpdateBeans(){BeanData.Update(goodBeans);goodBeans.Clear();badBeans.Clear();}publicvoidUpdateBeans(){BeanData.Update(goodBeans);goodBeans.Clear();badBeans.Clear();if (OnBeansUpdate != null)OnBeansUpdate();}publiceventActionOnBeansUpdate;
- 30. Code Coverage + Continuous IntegrationNot a silver bulletstill need to make sure that we are testing “the right” things, and not just hitting some magical numberstill need to make sure we have healthy testsPro tip
- 31. Code Coverage + Continuous IntegrationCreates a base line or smoke test to look forWatch trends over magic percent numbersPro tip
- 32. Code Coverage + Continuous IntegrationTeam City Code Coverage
- 33. Code Coverage + Continuous IntegrationSonar
- 34. Strategy #3
- 35. Strategy #3Divide and Conquer (pick your battles)
- 36. 36Commitment
- 37. 37 Raise your hand and repeat after me,Commitment
- 38. 38 Raise your hand and repeat after me,CommitmentI will not practice bad code.
- 41. “Resist Legacy Coupling”tight coupling = change anywhereaffects everythingLegacy MonsterProcessorStatic ConfigStatic ProxyProcessor SettingsData ConnectionsRules ConfigurationsNew FunctionalityCouplingNeeds IProxyCouplingstatic Config class leads to Heavy Weight testingCouplingCouplingCouplingRulesDatadon’t reference Config MonsterCouplinguse DI for only what you need (IProxy)
- 42. Introduce SOLID principals on new development… gradually improve code over timehttp://developingux.com/di/
- 43. wrap up
- 44. Know your Foe wrap upUse a Safety NetDivide and Conquer
- 46. Photo Credits© Michael Cummings - http://dreaminpictures.comhttp://www.flickr.com/photos/boogeyman13/2432667459/http://www.flickr.com/photos/stopthegears/50553611/http://www.flickr.com/photos/pochateca/324414459http://www.flickr.com/photos/27620885@N02/2594362917
Editor's Notes
- take a minute to have student “read” test and talk out what it’s doing.
- Build out slide.. Before you click through: take a minute to have student “read” test and talk out what it’s doing.