Seattle.rb - Refactoring & BDD Presentation

A presentation on code refactoring that I gave at Seattle.rb in October, 2012. There is also a behavioral driven development example from my work on the CapGun http://capgun.io/ service.

Transcript

1. Refactoring
   Mike Mondragon
   @monde
   Tuesday, January 8, 13
   

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2. Thank you Seattle.rb
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3. Refactoring?
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4. “Refactoring”
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5. “Refactoring”
   •Examples
   •Definition & Principles
   •Symptoms (Code Smells)
   •Testing
   •Catalog
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6. Why Refactor?
   •My code sucks
   •I don’t know what I’m doing
   •I don’t know what this code
   is doing
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7. Why Refactor?
   •Their code sucks
   •They don’t know what they
   are doing
   •I don’t know what their
   code is doing
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8. The less your problem is
   understood, the more
   complicated your solution is
   likely to be.
   Somebody Said This
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9. Refactoring
   •Modify code in small steps
   •Write tests for code that is
   affected
   •Write human readable code
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10. package.data.size == 0
    package.data.size < 12
    package.data.size == 12
    Example
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11. Example
    Logic defining the state of the
    object is contained outside of it
    package.data.size == 0
    package.data.size < 12
    package.data.size == 12
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12. package.data.size == 12 ||
    package.data.size == 13
    Example
    • Hard to find all places of code
    implementing outside logic
    • Object doesn’t control it’s own logical
    state
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13. Cat Picture
    -- (DO NOT WANT)
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14. Query? Method Pattern
    •Object tells you it’s state
    •Method is intention revealing
    •Is human readable
    •Examples: obj.nil? ... num.zero?
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15. Example
    Write tests first
    it "can be empty" do
    @package.empty?.must_equal true
    end
    it "can't be partial" do
    @package.partial?.must_equal false
    end
    it "can't be complete" do
    @package.complete?.must_equal false
    end
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16. Example
    Fail is good
    1) Error:
    test_0001_can_be_empty(Package):
    NoMethodError: undefined method `empty?' for #
    spec.rb:16:in `block (2 levels) in '
    2) Error:
    test_0002_can_t_be_partial(Package):
    NoMethodError: undefined method `partial?' for #
    spec.rb:20:in `block (2 levels) in '
    3) Error:
    test_0003_can_t_be_complete(Package):
    NoMethodError: undefined method `complete?' for #0x007fc304d93f18>
    spec.rb:24:in `block (2 levels) in '
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17. Example
    Implementation, State Is In A Single Location
    def empty?
    data.size.zero?
    end
    def partial?
    !empty? && data.size < 12
    end
    def complete?
    data.size == 12 || data.size == 13
    end
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18. I heard you like state so
    much, I put some ...
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19. Example
    Passing but ...
    # Running tests:
    Package#test_0002_can_t_be_partial = 0.49 s = .
    Package#test_0001_can_be_empty = 0.54 s = .
    Package#test_0003_can_t_be_complete = 0.98 s = .
    Finished tests in 2.007646s, 1.4943 tests/s, 1.4943 assertions/s.
    3 tests, 3 assertions, 0 failures, 0 errors, 0 skips
    wtf? 2 seconds
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20. Example
    Production data hardcoded into implementation :(
    def data
    JSON.parse(HTTParty.get(
    'http://goo.gl/4L1Zd'
    ))
    end
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21. Example
    Mock or override #data method in specs
    module SpecEmpty
    def data
    []
    end
    end
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22. Example
    Mock or override #data method in
    specs - clears away distractions
    before do
    @package = Package.new
    @package.extend(SpecEmpty)
    end
    it "can be empty" do
    @package.empty?.must_equal true
    end
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23. Example
    Passing and ...
    # Running tests:
    Package::empty#test_0002_can_t_be_partial = 0.00 s = .
    Package::empty#test_0001_can_be_empty = 0.00 s = .
    Package::empty#test_0003_can_t_be_complete = 0.00 s = .
    Finished tests in 0.000742s, 4043.1267 tests/s, 4043.1267 assertions/s.
    3 tests, 3 assertions, 0 failures, 0 errors, 0 skips
    fast! ~0 seconds
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24. Simple Mistakes Compound
    Upon Themselves
    • logic was external to object
    • external logic is hard to maintain/find
    • we had no tests
    • external data implementation had to be
    addressed in testing
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25. Pro-Tips
    • Refactoring Favors Behavior Rather Than
    Logic
    • Writing code that can be unit tested
    changes your writing style
    • If a method can’t be unit tested it must be
    refactored
    • Factor out interaction with frameworks
    from code that is tested
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26. Cat
    Picture
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27. Outside-In
    Let your tests drive your implementation
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28. Green Field Project
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29. Green Field Project
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30. This green field is already in
    production
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31. Green Field Project
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32. http://capgun.io/
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33. capgun.io
    API for web thumbs and web screens using
    headless webkit via PhantomJS/CasperJS
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34. CapGun Started Here
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35. So MANY Choices!
    • Sessions
    • Authentication
    • JSON rendering
    • Data Store(s)
    • ORM
    • framework(s)
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36. Start Somewhere
    Feature: Order Estimates
    As an API client
    In order to list information about orders
    I want to be able to query the order API
    Background:
    Given I am a valid API user
    And I send and accept JSON
    Scenario: getting an estimate for a base screen capping job
    When I send a POST request to "/api/v1/orders/estimate" with the following body:
    |{ "url": "http://example.com/cucumber#test" }|
    Then the response should be "200"
    And the JSON response should not have "order/job"
    And the JSON response should have an estimate of 1 credits
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37. Start Somewhere
    describe "Estimate" do
    describe "json" do
    should "estimate capping a URL for 1 credit" do
    post '/estimate.json',
    '{"url":"http://www.seattlerb.org/"}'
    JSON.parse(last_response.body).should == {
    'order' {
    'id' '4fd20a1288f560177600000a'
    'url' 'http://www.seattle.rb/'
    'cost' 1
    }
    }
    end
    end
    end
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38. Write Code That Is Used
    Immediately, Do Not Future Proof It
    class Order
    def cost
    end
    end
    describe Order do
    describe "defaults" do
    it "should cost 1 credit" do
    subject.cost.should == 1
    end
    end
    end
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39. Dog Food ASAP!
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40. Dog Food ASAP!
    http://tumblr.capgun.io/
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41. • Write Specs
    • Fail
    • Write Code
    • Pass
    • ????
    • Profit
    Iterate
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42. Outside-In / BDD is
    really just “poor man’s
    pair programming” *TM
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43. Thank You!
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44. Mike Mondragon
    •http://plasti.cx/
    •@monde Twitter
    •@monde Github
    •@monde coderwall
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45. Image Attribution
    @monde Gavatar by Mike Mondragon
    https://secure.gravatar.com/avatar/74c036cfbef785b139d06ccad4687b44?s=420&d=https://a248.e.akamai.net/assets.github.com%2Fimages%2Fgravatars%2Fgravatar-user-420.png
    Phil Hagelberg Seattle.rb shirt by veganstraightedge
    http://www.flickr.com/photos/veganstraightedge/7843002706/in/set-72157631203475428
    Amazon cover of “Refactoring” book
    http://www.amazon.com/Refactoring-Improving-Design-Existing-Code/dp/0201485672
    Wallace the cat cradled like a baby - Mike Mondragon
    Xzibit head shot - The Internet
    Wallace - THE INTERNETS is watching - Mike Mondragon on icanhazcheezburger
    Green field @ wallpaperstock.net
    http://wallpaperstock.net/green-field_wallpapers_8739_1024x768_1.html
    Palouse wheat field - unknown
    Palouse wheat field - unknown
    Tilled field - unknown
    CapGun logo - Mike Mondragon
    Skitch screen cap of CapGun panel - Mike Mondragon
    Tilled field - unknown
    Kitten asleep in food dish
    http://catlovingcare.com/2042/blog/loosing-weight-tips-for-fat-cats/2009/12/
    Skitch screen cap of http://tublr.capgun.io/ - Mike Mondragon
    CapGun.io result for Seattlerb.org - Mike Mondragon
    Wallace the cat profile - Mike Mondragon
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