2019-chicago-jug-mutation-testing.pdf

Transcript

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   @jeanneboyarsky 1 Intro to Mutation Testing Jeanne Boyarsky Monday, November

   4, 2019 Chicago Java User Group speakerdeck.com/boyarsky
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   @jeanneboyarsky Shout out to the selection process! 2

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   @jeanneboyarsky Pause for a Commercial 3

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   @jeanneboyarsky Why write tests? 4 It used to work!

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   @jeanneboyarsky How know if tests are good? 5

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   @jeanneboyarsky If test coverage low 6 Write more tests! Not

   ready for mutation testing of class
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   @jeanneboyarsky If test coverage high 7 All done! Perfect code!

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   @jeanneboyarsky Or is it? 8 Why is it saying nobody

   is registered?
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   @jeanneboyarsky Code Review! 9

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    @jeanneboyarsky That’s a mutant! 10

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    @jeanneboyarsky Too many mutants! 11 They’re everywhere!

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    @jeanneboyarsky PIT to the rescue! 12

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    @jeanneboyarsky What is PIT? • Originally Parallel Isolated Test •

    Now just PIT 13
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    @jeanneboyarsky Easy to run 14

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    @jeanneboyarsky Easy to run 15

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    @jeanneboyarsky The console flies by 16

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    @jeanneboyarsky We caught 5 mutants 17

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    @jeanneboyarsky More detail 18

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    @jeanneboyarsky The mutants live…. 19

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    @jeanneboyarsky Level up 20

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    @jeanneboyarsky Now 32 survived 21

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    @jeanneboyarsky PIT 22 Mutant Generation Bytecode (ASM) Test Selection Coverage

    Mutant Insertion Instrumentation Mutant Detection Early Exit (fine)
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    @jeanneboyarsky Mutant Generation Options 1. Bytecode • Faster • May

    not map to line of code • Java 8 stream support was immediate 2. Source Code • Slower • Clearer 23 Thank you to pitest.org for this material
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    @jeanneboyarsky Test Selection Options 1. Coverage • Fast - picks

    right test 2. Naive • Slow - brute force 3. Convention • Medium - uses naming conventions 24 Thank you to pitest.org for this material
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    @jeanneboyarsky Mutant Insertion Options 1. Instrumentation • Fast - picks

    right test 2. Classloader • Uses a lot of memory 3. Debugger Hotswap • Can be slower because debugger on 25 Thank you to pitest.org for this material
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    @jeanneboyarsky Mutant Detection Options 1. Early Exit (fine) • Stops

    when test finds a mutant 2. Early Exit (coarse) • Stops when class finds a mutant 3. Naive • Slow - brute force 26 Thank you to pitest.org for this material
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    @jeanneboyarsky JUnit 5 Support • PitClipse assigned to next version

    on Oct 5 27
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    @jeanneboyarsky JUnit 5 Support • No date for IntelliJ 28

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    @jeanneboyarsky JUnit 5 Support • Supported by • Maven •

    Gradle • However…. I find IDE integration to be critical 29
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    @jeanneboyarsky Tips • JUnit tests must pass • Watch console

    to see if still running • Reports on whole project • Fixing one may take care of more 30
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    @jeanneboyarsky For More • Code Kata: https://github.com/vmzakharov/mutate- test-kata 31

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    @jeanneboyarsky Demo 32