2017 JavaOne Mutation Testing Session
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This document is an introduction to mutation testing presented by Jeanne Boyarsky. The presentation covers what mutation testing is, includes a live demo, and discusses different types of mutants that can be tested for. The goal is to use mutation testing to improve test quality by introducing faults into code to ensure tests can detect those faults.
2017 JavaOne Mutation Testing Session
- 1. Intro to Mutation Testing (CON 1694) slideshare.net/boyarsky Twitter @jeanneboyarsky Blog: http://www.selikoff.net Jeanne Boyarsky JavaOne - October 5, 2017
- 2. @jeanneboyarsky About Me 15 years as •Java Developer •JUnit user
- 3. The Plan 1. About mutation testing 2. Live demo 3. A look at types of mutants 4. Profit??? @jeanneboyarsky
- 4. Why write tests? @jeanneboyarsky It used to work!
- 5. How know if tests are good? @jeanneboyarsky
- 6. If test coverage low @jeanneboyarsky Write more tests! Not ready for mutation testing of class
- 7. If test coverage high @jeanneboyarsky All done! Perfect code!
- 8. Or is it?Why is it saying nobody is registered? @jeanneboyarsky
- 12. PitClipse to the rescue! @jeanneboyarsky
- 14. JUnit 5 • Unofficial Fork: https://github.com/tobiasstadler/pitest-junit5-plugin • It’s coming: https://github.com/hcoles/pitest/issues/284 https://github.com/hcoles/pitest/issues/398 @jeanneboyarsky
- 16. The console flies by @jeanneboyarsky
- 17. Wait, we just had 100% coverage @jeanneboyarsky
- 18. We caught 5 mutants @jeanneboyarsky
- 23. Observations • JUnit tests must pass • Fixing one may take care of more • Found a bug • Better tests @jeanneboyarsky
- 24. Now with all mutators @jeanneboyarsky
- 25. Observations • Better tests • Unused production code @jeanneboyarsky
- 26. Examples of Conditional Mutants @jeanneboyarsky Conditionals Boundary <= vs < Negative Conditionals <= vs > Void Method Call Removes method calls
- 27. Examples of Math Mutants @jeanneboyarsky Math * vs / Increments ++ vs -- Invert Negatives x vs -x
- 28. Examples of Other Mutants @jeanneboyarsky Return Values x vs x+1 Disabled by default (false positives, duplicates or crashes) Constructor Calls Inline Constants Non Void Method Calls Remove Conditionals Experimental Member Variables Switch
- 29. Tips for bigger projects • Watch console to see if still running • Reports on whole project – drill down/split up • Exclude long running tests • Experimental feature: incremental analysis @jeanneboyarsky
- 31. More info • http://pitest.org/ • https://github.com/philglover/pitclipse • https://dzone.com/articles/introduction-mutation @jeanneboyarsky
- 32. @jeanneboyarsky
Editor's Notes
- #4: https://cdn.pixabay.com/photo/2012/05/07/05/18/bug-48020_1280.png https://pixabay.com/p-303966/?no_redirect
- #5: https://cdn.pixabay.com/photo/2012/05/07/05/18/bug-48020_1280.png https://pixabay.com/p-303966/?no_redirect
- #6: http://www.eclemma.org/jacoco/trunk/coverage/
- #7: https://pixabay.com/p-149251/?no_redirect
- #9: https://pixabay.com/p-1300226/?no_redirect
- #11: http://www.publicdomainpictures.net/pictures/180000/velka/mutant-female-41.jpg
- #12: http://orig01.deviantart.net/920f/f/2015/013/a/8/teenage_mutant_ninja_turtles__2003__drawing__by_n0rvv3g14n_g1rl-d8drynd.jpg
- #14: Image sources: https://commons.wikimedia.org/wiki/File:Antu_netbeans-ide.svg https://commons.wikimedia.org/wiki/File:Eclipse-SVG.svg https://commons.wikimedia.org/wiki/File:IntelliJ_IDEA_Logo.svg https://ant.apache.org https://maven.apache.org http://junit.org/junit4/
- #23: Run initially Add 2 assertTrue and one assertFalse on tooManyAttendees – incorrectly to show failure with failing unit tests. Wait there’s a bug. Fix assertions and see down to three mutants In cancel test assertFalse on my registration now down to two mutants Then add assertTrue on Barry’s registration and see all mutants killed
- #25: Change to all mutators Run initially and note that down from 23 to 7 – our tests are better Note that the wait list logic still isn’t tested enough. Add test for jeanne and maurice cancelling with barry and sai on wait list with four asserts 4 mutants left Add test for sai not on wait list so wait list empty 2 mutants left These two are interesting as they point to unused code – isRoomForMoreAttendees always true and don’t use company name (attendee map value)
- #33: https://commons.wikimedia.org/wiki/File:Online_Survey_Icon_or_logo.svg