Achieving peace of mind through test coverage

In this talk we are going to see how to efficiently implement tests in order to achieve a consistent and reliable release strategy that will allow all your team members to sleep at night.

Presented at http://js-montreal.org/ meetup of October 2019.

Git repo containing the demo presented can be find here: https://github.com/ruyadorno/the-one-with-test-coverage

Transcript

1. Achieving peace
   of mind through
   test coverage
   js-montreal 10/2019
   

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2. Ruy Adorno
   @ruyadorno
   OSS Dev @
   

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4. Intro
   Tests are an essential tool that helps alleviate the
   task of maintaining a code base. They give us
   confidence when shipping new releases of a program
   by providing an automate assessment into its
   expected set of features.
   My hope with this talk is to enlighten on how
   coverage of code is important and provide practical
   tips on how to test more of your code.
   

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5. What is a test?
   • Program that runs your code
   • Validates your expectations
   • Makes sure things behave the
   way they should
   

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6. Benefits:
   • Reliability, you want to know about
   defects as soon as possible
   • Approachability, people can tweak
   your code and know if they break it
   • Quality, teams end up finding
   improvements and optimizations
   

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7. Coverage
   • Metric, it tracks what parts of
   your program actually executed
   • Doesn’t prove that the test
   suite is good
   • That can serve as a test itself
   

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8. Benefits:
   • In order to achieve higher coverage you
   have to dig deeper into the internals
   • Help to uncover bugs, serves as
   documentation to all program details
   • Serves as confidence meter for that code
   

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9. Mergebot
   • Github bot
   • Controls merging PRs
   • Front End cli scripts
   

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10. • Let’s go through some examples of
    helpful patterns while trying to bump
    test coverage
    Useful patterns:
    

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11. Snapshots
    

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12. Snapshots
    • Useful when testing verbose output
    • pros: Extra convenient to work with
    • cons: requires way more discipline
    

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13. Patch APIs
    

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14. Patch APIs
    • Allow us to assert for specific
    internal calls (specially global)
    

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15. Abstractions
    

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16. Abstractions
    • Abstract hard to test internals
    into separated function/modules
    

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17. Mocking modules
    

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18. Mocking modules
    • Cleaner solution to checking to
    internal calls
    • Test frameworks tend to provide
    simpler to use APIs for those
    

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19. node-tap
    

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20. node-tap
    • Different test frameworks provide a
    different set of APIs but conceptually
    they all share the same ideas
    

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21. node-tap
    

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22. node-tap
    • One very convenient design choice of
    node-tap is allowing to run tests
    without the need of a top-level runner
    • Makes it so much easier to start
    debugging your tests
    

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23. It may be difficult to get coverage up, specially
    when reaching to parts of your codebase in which are
    harder to test by the very nature of the code there.
    I hope the patterns I share here help you on the
    task of covering more features of your code base
    using automated tests.
    Conclusion:
    

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24. process.exit(0)
    https://ruyadorno.com
    Thanks!
    

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25. Photo Credits
    • Photo by Kari Shea on Unsplash
    • Photo by Grzegorz Mleczek on Unsplash
    • Photo by rawpixel on Unsplash
    • Photo by Aidan Hancock on Unsplash
    

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