How to test untestable code
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How to test legacy code with hardwired dependencies. This talk explains how to deal with legacy code wisely. This presentation should be done with a live code based on the TripService Kata created by Sandro Mancuso.
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How to test untestable code
- 1. HOW TO TEST UNTESTABLE CODE Bruno BOUCARD @brunoboucard #LearnToCraft
- 2. THE PROBLEM NEED TO BE REFACTORED NOT DESIGNED TO BE TESTABLE
- 3. WHY? NOT DESIGNED TO BE TESTABLE Hardwired dependencies Database Network connection Third service Real time Random Singletons Statics
- 4. FACT - LEGACY CODE IS NOT DESIGNED TO BE TESTABLE
- 5. FACT - LEGACY CODE IS NOT DESIGNED TO BE TESTABLE
- 6. DON’T BE AFRAID BY A DAUNTING SITUATION SO, HOW TO START?
- 7. DON’T BE AFRAID BY A DAUNTING SITUATION SO, HOW TO START? Many classes Many lines of code Many warnings from Code Metrics Never built with testability in mind
- 8. CLEAN THE DECK HOW TO START?
- 9. CLEAN THE DECK HOW TO START? Delete commented out and unused code Makes the code easier to understand You don’t want to write unnecessary tests Tools like Resharper for .NET can help The compiler is a reliable ally Remember you have version control for emergencies (hopefully)
- 10. DO NOT ATTEMPT A BIG BANG HOW DO I KNOW THAT I‘M NOT BREAKING ANYTHING?
- 11. DO NOT ATTEMPT A BIG BANG HOW DO I KNOW THAT I‘M NOT BREAKING ANYTHING? Changing all the code to add unit tests Will break everything! Start small and work outwards Velocity will be low initially Should increase as test coverage increases Use code coverage as a useful metric But don’t be enslaved by it
- 12. HOW DO I KNOW THAT I‘M NOT BREAKING ANYTHING? MOVE ON CAREFULLY
- 13. HOW DO I KNOW THAT I‘M NOT BREAKING ANYTHING? MOVE ON CAREFULLY Hyperaware Editing Preserve Signatures Single-Goal Editing Lean on Compiler Pair Programming
- 14. LIVE CODE TRIPSERVICE SHARED YOUR TRIP AND HAVE FUN Source : Sandro Mancuso https://www.youtube.com/watch?v=_NnElPO5BU0
- 15. Bruno BOUCARD @brunoboucard #LearnToCraft DON’T BE AFRAID BY A DAUNTING SITUATION CLEAN THE DECK DO NOT ATTEMPT A BIG BANG MOVE ON CAREFULLY APPLY BREAKING DEPENDENCIES TECHINQUES HOWTOSTARTHOWTONOTBREAKANYTHING? INSUMMARY