Mutation Testing with Mutant

Tests are a good tool to verify your code but how do you verify your tests? Mutation testing is a technique to evaluate the quality of your tests by programmatically mutating (i.e. making a series of small modifications to) your code and ensuring that the tests no longer pass. This talk will attempt to demonstrate the value of mutation testing and show you how to use Mutant to improve the quality of your tests and your code.

Transcript

1. flickr.com/photos/tomtolkien
   Mutation
   Testing with
   Mutant
   

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2. A carpenter
   is only as good
   as their tools.
   flickr.com/photos/matthigh
   

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3. What’s in
   your toolbox?
   flickr.com/photos/dk_spook
   

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4. Editor
   flickr.com/photos/audringje
   

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5. flickr.com/photos/laughingsquid
   Vim 1.0
   

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6. Debugger
   flickr.com/photos/86639298@N02
   

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7. Profiler
   flickr.com/photos/anndouglas
   

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8. Testing
   

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9. Testing
   flickr.com/photos/onepointfour
   

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10. Code has bugs
    Tests are code ∴
    Tests have bugs
    flickr.com/photos/birdseyeview
    

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11. Code Coverage
    

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12. twitter.com/bloerwald/status/448415935926255618
    

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13. Mutation
    flickr.com/photos/tambako
    

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14. Original
    def foo(arg = true)
    arg || fail
    end
    assert_nothing_raised { foo }
    

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15. Mutant
    def foo(arg = true)
    arg
    end
    assert_nothing_raised { foo }
    

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16. twitter.com/kytrinyx/status/453567958317428736
    

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17. Demo
    

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