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Unit Testing Done Right
- 1. Unit testing doneright
- 2. whoami • Brian Fenton •Bigcommerce • @brianfenton • Mostly PHP and APIs
- 3. What is aunit test? • Small • Fast • Tests a single unit <- Here there be dragons
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- 6. “A single pieceof a class’s public-facing functionality”
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- 8. Goals of unittesting over time • Find bugs • Find regressions • Improve design
- 9. Philosophies • Traditional testing •TDD • XP • BDD
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- 12. How did weget here?
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- 14. "When a measurebecomes a target, it ceases to be a good measure.” - Goodhart’s Law
- 15. Different kinds ofcoverage • Line • Function/Method • Class/Trait
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- 17. Coverage tricks • if(false) this_function_call_is_covered(); • // @codeCoverageIgnore • multiple checks on the same line
- 18. Line coverage canonly prove code wasn’t executed
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- 20. Example for ($i = 0; $i > 10; $i++) { if ($i % 2 === 0) { echo "Even: "; } else { echo "Odd: "; } echo $i, "n"; }
- 21. More kinds ofcoverage • Opcode • Branch • Path
- 23. Testing your privates •Don’t! • Extract functionality to a collaborator or don’t test it
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- 27. Flaky tests • Randomness •Time/environment • Network/services
- 28. Randomness • Can therandomness come from outside? • Do you need to know the exact value? • Can you just verify “randomness”?
- 29. Namespace trick namespace MyNamespace; function random() { return mt_rand(); }
- 30. Namespace trick namespace MyNamespace { function random() { return 7; } } namespace MyTests; … function testRandomNumberGenerator() { $this-‐>assertSame(7, random()); }
- 31. Environment • Time • Shellvars/ini settings/config values • Filesystem
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- 33. Good unit tests •Single reason to fail • Clearly named • testGuestCanRegisterWithValidInformation • testProcessData
- 34. Good unit tests •Easy to read • Clean • Arrange, Act, Assert
- 35. Good unit tests •Fast • No side effects
- 36. Listening to yourtests
- 37. Test smells • Toomany mocks • Lots of setup required • Can’t test w/o database/network/etc… • Can’t inject mocks where needed
- 38. Test smells • Mocksreturning mocks • Flaky results • Unrelated code changes breaking tests • Testing the implementation
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