Unit Testing: What? Why? How?

Slides from my talk at WP Hooked, February 2017.

https://www.meetup.com/wp_hooked/

Transcript

1. Unit Testing:
   What? Why? How?
   

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2. John Blackbourn
   WordPress core developer
   Working with WordPress for 10+ years
   Senior Engineer at Human Made
   @johnbillion
   

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3. Unit Testing:
   What? Why? How?
   

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4. You’re Going to
   L VE
   Unit Testing
   

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5. That’s Enough
   of That
   

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6. Unit Testing:
   What? Why? How?
   

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7. A unit test is a piece of code
   which exists only to verify expectations
   about the behaviour of another piece of code
   Verification
   

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8. a.k.a.
   “Does my function do
   what I expect it to do?”
   

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9. A unit test operates in isolation
   in order to avoid external interference
   Isolated
   

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10. Tests typically run on the command line
    CLI
    

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11. Tests are highly efficient
    because they're quickly repeatable
    Automated
    

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12. Crossing your fingers
    and hoping…
    is not a unit test
    

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13. Unit Testing:
    What? Why? How?
    

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14. A unit test can cover many scenarios
    and never misses anything
    Accuracy
    

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15. Unit tests give you increased assurance
    that changes are less likely to cause breakage
    Assurance
    

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16. Unit tests give you
    confidence to make changes
    Confidence
    

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17. Unit tests help you write better code
    Smaller functions
    Separation of concerns
    Quality
    

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18. Unit tests can be liberating
    Clarity
    

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19. Unit Testing:
    What? Why? How?
    

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24. “But I know that false isn’t true”
    

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26. Arrange
    Act
    Assert
    AAA
    

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27. Each time a WordPress test runs,
    it operates on a fresh installation
    Remember
    

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32. Accuracy
    Assurance
    Confidence
    Quality?…
    The Result
    

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33. Assertions
    assertTrue( $actual )
    assertFalse( $actual )
    assertEquals( $expected, $actual )
    assertCount( $expected, $actual )
    assertObjectHasAttribute( $key, $actual )
    assertArrayHasKey( $key, $actual )
    assertWPError( $actual )
    assertCanonical( $actual, $expected )
    

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34. a.k.a.
    A Real World Gotcha
    Type Juggling Kills Me
    

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37. WUT
    

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39. Provide Verification
    Isolated
    Automated
    Recap
    

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40. Accuracy
    Assurance
    Confidence
    Quality
    Recap
    

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41. Arrange
    Act
    Assert
    Recap
    

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42. I Hope You’ll Fall
    In L VE
    With Testing
    

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43. Read the WordPress Unit Tests
    Visit PHPUnit website for reference
    Check out WP-CLI scaffolding
    What Next?
    

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44. John Blackbourn
    @johnbillion
    

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