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Breaking up (with) your test suite poa asd

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My name is Justin Searls Please tweet me @searls & Say [email protected]

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Any questions? Tweet @searls during the talk Favorite question gets a book!

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Any questions? Tweet @searls during the talk Favorite question gets a book!

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This talk is about z aPPOOIU

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This talk is about z aPPOOIU relationships

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I my customers ias al

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I coding zffrttyu z

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I testing aske zc

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We don't test for testing's sake rRth asd

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I get paid for code that works, not for tests, so my philosophy is to test as little as possible to reach a given level of confidence. - Kent Beck asdz ty

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We don't code for code's sake, either mmmmznxdfr lr

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Writing code is a costly way to solve problems oiz eu

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Too often, we cheat on our customers with our code c d aoiey

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How to cheat on your customers: ae ts

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How to cheat on your customers: ae ts 1. Uncritically assume your favorite way to write code applies to every situation

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How to cheat on your customers: ae ts 1. Uncritically assume your favorite way to write code applies to every situation 2. There is no #2

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evh zc Cargo-culting as a service

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We must challenge our biases in each new context to grow fh ywe

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iO ZOe infatuation

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xmt iRosXc Remember TATFT?

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TDD literally rescued me from the pit of despair.

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lzxcm zxcmlzcl lzxckz zxczc zxjcozcjoe AOO asodjaosd encz caosdjojo jojo 6 months later ~ ~

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Why does every refactor break 6 tests?!

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Why does the build take nine hours to run?!

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Why are people mocking methods on the object they're testing?!

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Why can't we get anything done anymore?

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asodo zoxjcz aoo ueue yyyz cxjk zxcczx and eventually ~ ~

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the break-up

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the break-up

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$ the break-up

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$ the break-up rm -rf spec features

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jn poi introspection

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qwer bvt Why test?

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No content

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!

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! !

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! !

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! ! !

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! ! !

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! ! !

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! ! ! !

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! ! ! ! !

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! ! ! ! !

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! ! ! ! ! !!

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! ! ! ! ! !! ! ! ! !

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! ! ! ! ! !! ! ! ! ! Confidence

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! ! ! ! ! !! ! !!

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! ! ! ! ! !! Understanding ! !!

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mni pl Single Responsibility Testing

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describe "Panda" do end

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describe "Panda" do let(:bamboo) { double("bamboo").as_null_object } end

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describe "Panda" do let(:bamboo) { double("bamboo").as_null_object } subject { Panda.new(bamboo) } end

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describe "Panda" do let(:bamboo) { double("bamboo").as_null_object } subject { Panda.new(bamboo) } ! it "munches bamboo" do end end

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describe "Panda" do let(:bamboo) { double("bamboo").as_null_object } subject { Panda.new(bamboo) } ! it "munches bamboo" do subject.eat! end end

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describe "Panda" do let(:bamboo) { double("bamboo").as_null_object } subject { Panda.new(bamboo) } ! it "munches bamboo" do subject.eat! expect(bamboo).to have_received(:munch) end end

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describe "Panda" do let(:bamboo) { double("bamboo").as_null_object } subject { Panda.new(bamboo) } ! it "munches bamboo" do subject.eat! expect(bamboo).to have_received(:munch) end end

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asdj zoxc mmr qu psoi rnzc vnkl la later, fixing a bug ~ ~

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describe "Panda" do let(:bamboo) { double("bamboo").as_null_object } subject { Panda.new(bamboo) } ! it "munches bamboo" do subject.eat! expect(bamboo).to have_received(:munch) end end

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describe "Panda" do let(:bamboo) { Bamboo.find(34) } subject { Panda.new(bamboo) } ! it "munches bamboo" do subject.eat! expect(bamboo).to have_received(:munch) end end

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describe "Panda" do let(:bamboo) { Bamboo.find(34) } subject { Panda.new(bamboo) } ! it "munches bamboo" do allow(bamboo).to receive(:munch) subject.eat! expect(bamboo).to have_received(:munch) end end

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describe "Panda" do let(:bamboo) { Bamboo.find(34) } subject { Panda.new(bamboo) } ! it "munches bamboo" do allow(bamboo).to receive(:munch) subject.eat! expect(bamboo).to have_received(:munch) end ! it "returns bamboo id" do end end

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describe "Panda" do let(:bamboo) { Bamboo.find(34) } subject { Panda.new(bamboo) } ! it "munches bamboo" do allow(bamboo).to receive(:munch) subject.eat! expect(bamboo).to have_received(:munch) end ! it "returns bamboo id" do expect(subject.eat!).to eq(34) end end

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describe "Panda" do let(:bamboo) { Bamboo.find(34) } subject { Panda.new(bamboo) } ! it "munches bamboo" do allow(bamboo).to receive(:munch) subject.eat! expect(bamboo).to have_received(:munch) end ! it "returns bamboo id" do expect(subject.eat!).to eq(34) end end

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asdj zoxc mmr qu psoi rnzc vnkl la one day, I find it ~ ~

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describe "Panda" do let(:bamboo) { Bamboo.find(34) } subject { Panda.new(bamboo) } ! it "munches bamboo" do allow(bamboo).to receive(:munch) subject.eat! expect(bamboo).to have_received(:munch) end ! it "returns bamboo id" do expect(subject.eat!).to eq(34) end end

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describe "Panda" do let(:bamboo) { Bamboo.find(34) } subject { Panda.new(bamboo) } ! it "munches bamboo" do allow(bamboo).to receive(:munch) subject.eat! expect(bamboo).to have_received(:munch) end ! it "returns bamboo id" do expect(subject.eat!).to eq(34) end end ? ? ?

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describe "Panda" do let(:bamboo) { Bamboo.find(34) } subject { Panda.new(bamboo) } ! it "munches bamboo" do allow(bamboo).to receive(:munch) subject.eat! expect(bamboo).to have_received(:munch) end ! it "returns bamboo id" do expect(subject.eat!).to eq(34) end end ? ? ?

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describe "Panda" do let(:bamboo) { Bamboo.find(34) } subject { Panda.new(bamboo) } ! it "munches bamboo" do allow(bamboo).to receive(:munch) subject.eat! expect(bamboo).to have_received(:munch) end ! it "returns bamboo id" do expect(subject.eat!).to eq(34) end end ? ? ? Why does this test exist?

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describe "Panda" do let(:bamboo) { Bamboo.find(34) } subject { Panda.new(bamboo) } ! it "munches bamboo" do allow(bamboo).to receive(:munch) subject.eat! expect(bamboo).to have_received(:munch) end ! it "returns bamboo id" do expect(subject.eat!).to eq(34) end end ? ? ? Why does this test exist? What type of test is this?

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describe "Panda" do let(:bamboo) { Bamboo.find(34) } subject { Panda.new(bamboo) } ! it "munches bamboo" do allow(bamboo).to receive(:munch) subject.eat! expect(bamboo).to have_received(:munch) end ! it "returns bamboo id" do expect(subject.eat!).to eq(34) end end ? ? ? Why does this test exist? How should tests be written? What type of test is this?

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nini lkre We should know these answers before opening the test!

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drt byby The purpose, rules, and structure of each test should be immediately clear

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kpo qw A single test can't address all of our motivations

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zxc eqr Such tests are unclear:

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zxc eqr • purpose is hazy Such tests are unclear:

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zxc eqr • purpose is hazy • rules are debatable Such tests are unclear:

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zxc eqr • purpose is hazy • rules are debatable • structure is ad hoc Such tests are unclear:

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tyu fd Unclear tests cost money

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awe voOa Unclear tests must constantly have their:

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awe voOa Unclear tests must constantly have their: • purpose rediscovered

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awe voOa Unclear tests must constantly have their: • purpose rediscovered • rules renegotiated

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awe voOa Unclear tests must constantly have their: • purpose rediscovered • rules renegotiated • structure reorganized

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xmcu peo None of those activities have value!

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ae r Every suite should promote at most type of confidence

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ae r Every suite should promote at most type of confidence

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c z Every suite should promote at most type of understanding

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c z Every suite should promote at most type of understanding

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suite design zxcm nz

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oeiz jdk Omakase Rails

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oeiz jdk Omakase Rails MiniTest

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oeiz jdk Omakase Rails Views MiniTest

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oeiz jdk Omakase Rails Views MiniTest MiniTest

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oeiz jdk Omakase Rails Controllers Views MiniTest MiniTest

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oeiz jdk Omakase Rails Controllers Views MiniTest MiniTest MiniTest

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oeiz jdk Omakase Rails Controllers Views Models MiniTest MiniTest MiniTest

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oeiz jdk Omakase Rails Controllers Views Models MiniTest MiniTest MiniTest

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ri xc Prime Rails

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ri xc Prime Rails Cucumber

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ri xc Prime Rails UI Cucumber

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ri xc Prime Rails RSpec UI Cucumber

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ri xc Prime Rails Views RSpec UI Cucumber

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ri xc Prime Rails Views RSpec RSpec UI Cucumber

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ri xc Prime Rails Controllers Views RSpec RSpec UI Cucumber

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ri xc Prime Rails Controllers Views RSpec RSpec RSpec UI Cucumber

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ri xc Prime Rails Controllers Views Models RSpec RSpec RSpec UI Cucumber

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ri xc Prime Rails Controllers Views Models RSpec RSpec RSpec UI Cucumber

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zpo qw "Fast Specs" Rails Controllers Views Models RSpec RSpec RSpec UI Cucumber

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zpo qw "Fast Specs" Rails Controllers Views Models RSpec RSpec RSpec UI Cucumber RSpec

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POROs zpo qw "Fast Specs" Rails Controllers Views Models RSpec RSpec RSpec UI Cucumber RSpec

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What's the problem? rRth asd

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Redundant test coverage rRth asd

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ri xc One model change Controllers Views Models RSpec RSpec RSpec UI Cucumber

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ri xc One model change Controllers Views Models RSpec RSpec RSpec UI Cucumber

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ri xc One model change Controllers Views Models RSpec RSpec RSpec UI Cucumber

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ri xc One model change Controllers Views Models RSpec RSpec RSpec UI Cucumber

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ri xc One model change Controllers Views Models RSpec RSpec RSpec UI Cucumber

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ri xc One model change Controllers Views Models RSpec RSpec RSpec UI Cucumber

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ri xc One model change Controllers Views Models RSpec RSpec RSpec UI Cucumber

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Which leads to: rRth asd

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ji cnzm Controllers Views Models UI RSpec (›°□°ʣ›ớ ᵲᴸᵲ Rails

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No content

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architecture jd qr

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+ -

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+ - app

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+ - router web app #1 web app #2 walrus data panda data cage control service

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+ - router walrus data panda data web front- end web back- end web app #1 cage control service

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+ - walrus data web backend panda data router Feed Zoo Animals Build Feed Plan Provide Meal Fetch Schedule Plan Meal Animal Adapter Compute Portions cage control service Release Food Cage Adapter

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+ - class ProvidesMeal def initialize... ! def provide(plan) @releases_food.release( @computes_portion.compute(plan) ) end end provides_meal.rb

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suite design slp er

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+ - class ProvidesMeal def initialize... ! def provide(plan) @releases_food.release( @computes_portion.compute(plan) ) end end provides_meal.rb

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+ - walrus data web backend panda data router Feed Zoo Animals Build Feed Plan Provide Meal Fetch Schedule Plan Meal Animal Adapter Compute Portions cage control service Release Food Cage Adapter

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+ - router walrus data panda data web front- end web back- end web app #1 cage control service

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+ - router web app #1 web app #2 walrus data panda data cage control service

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+ - app

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+ -

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The greatest test of all: dk rrt

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Does our software serve its purpose? qwe rtb

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Wait… what is its purpose? zl dfr

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Generating revenue? asd er

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Cutting costs? eit dfp

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Limiting our liability? xcg ke

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Funding non-profits? xd asdasdrg

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Can we write a test for those outcomes? zc er

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Maybe!* zc er

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Maybe!* zc er *But not in this talk.

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+ -

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+ - app

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Smoke tests oi fg app

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Acceptance tests zxc cxoije app

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Feature tests rv cm app

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End-to-end tests zoc qwe app

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Integration tests xu vll app

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Integration tests xu vll app

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as cjhf app Smoke Acceptance Feature End-to-end

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a cv app Smoke Acceptance Feature End-to-end

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ed cx app S A F E

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zfh ie app SAFE tests

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The test's "user"

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Confidence sought

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Understanding gained

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Guidelines

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Warning Signs

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app ec ze

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SAFE

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A real-world user SAFE

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web apps app SAFE

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http services app $ curl http:// SAFE

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SAFE

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Application works when it's all glued together SAFE

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SAFE

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"How simple is our product?" SAFE

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Can't fit your tests in 30 minutes? SAFE

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Can't fit your tests in 30 minutes? SAFE The app is complex

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SAFE Can't write a test in 30 minutes?

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SAFE Can't write a test in 30 minutes? The app is complicated

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SAFE

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SAFE tests shouldn't know internal APIs SAFE

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Web tests should bind to user-visible text, not markup SAFE

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Enforce a fixed-time budget SAFE

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Time-box the suite 5 minutes 5 minutes SAFE

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Time-box the suite 5 minutes 5 minutes monthly financials SAFE

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Time-box the suite 5 minutes 5 minutes monthly financials search SAFE

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Time-box the suite 5 minutes 5 minutes monthly financials process order search SAFE

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Time-box the suite 5 minutes 5 minutes monthly financials process order ad words search SAFE

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Time-box the suite 5 minutes 5 minutes sign-up monthly financials process order ad words search SAFE

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Time-box the suite 5 minutes 5 minutes sign-up monthly financials process order ad words search daily deals SAFE

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Time-box the suite 5 minutes 5 minutes sign-up monthly financials process order ad words search daily deals ? SAFE

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SAFE

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SAFE Failures due to refactors are false negatives

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SAFE Beware: human intuition overvalues "realistic" tests

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SAFE Building multiple releases & branches is expensive

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SAFE Superlinear Slowdown

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SAFE Superlinear Slowdown More tests Slower build

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SAFE Superlinear Slowdown

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SAFE Superlinear Slowdown Bigger System Slower build

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! ! ! ! ! !! SAFE

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! ! ! ! ! !! SAFE

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! ! ! ! ! !! SAFE

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+ - app

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+ - router web app #1 web app #2 walrus data panda data cage control service

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+ - router walrus data panda data web front- end web back- end web app #1 cage control service

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Good SAFE tests are accurate ef zc

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But they're also expensive asd tg

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And they don't inform our public API's design ef gi

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Every library or service you write is consumed by somebody tg gz

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Verify behavior & demonstrate usage with Consumption tests rRth asd

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Consumption

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Your 's consumer Consumption

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Your 's consumer Consumption service

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Your 's consumer Consumption library

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Your 's consumer Consumption user interface

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Your 's consumer Consumption repository

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Consumption

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Verifies behavior you're directly responsible for Consumption

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Consumption

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Answers: "Is it usable?" Consumption

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If it's hard to test, then it's hard to use Consumption

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Consumption

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Module boundaries should be meaningful beyond testing Consumption

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Consumption Fakes all external dependencies

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Consumption Fakes all external dependencies (i.e. can run without access to other services)

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Consumption Fakes all external dependencies (i.e. can run without access to other services) (e.g. in Travis CI)

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Exercises public, not private APIs Consumption

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Organized by consumers' desired outcomes Consumption

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Consumption

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Keep consumption tests really fast Consumption

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faked services Consumption no good reason to be slow

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The only suite that says you just broke something Consumption

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! ! ! ! ! !! Consumption

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! ! ! ! ! !! Consumption

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! ! ! ! ! !! Consumption

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+ - router walrus data panda data web front- end web back- end web app #1 cage control service

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+ - router web app #1 web app #2 walrus data panda data cage control service

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"If my tests fake out WalrusService how can I trust that GET /walruses still returns walruses?" xc r

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Why not test across service boundaries? q od

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Inter-service tests are easy! cd fe

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Inter-service tests are easy! cd fe 1. Start by not writing them

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Inter-service tests are easy! cd fe 1. Start by not writing them 2. Continue to not write them

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Inter-service tests are easy! cd fe 1. Start by not writing them 2. Continue to not write them 3. You're already done. Easy!

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qwe sd Inter-service tests are tempting, but they're .

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Inter-service tests are tempting, but they're . hard to set up qwe sd

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Inter-service tests are tempting, but they're . slow to run qwe sd

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Inter-service tests are tempting, but they're . redundant coverage qwe sd

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The root question indicates a lack of trust aie wq

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Default to trusting your depended-on services zxc see

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... but sometimes trust isn't appropriate! poae fg

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Sometimes our usage is abnormal or unsupported xcg asd

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Sometimes other teams demonstrate blind-spots iocv hgt

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When trust isn't enough, try writing Contract tests zx rrr

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Contract

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The "user" is us! Contract

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Test is written to represent your interests in somebody else's repo Contract

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Your needs become part of their Consumption suite Contract

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If they break your test, they know to call you! Contract

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Speedier Feedback Contract fast slow

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Speedier Feedback Contract production release fast slow

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Speedier Feedback Contract production release git push fast slow

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Contract

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Dependencies that we own behave how we need them to Contract

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Contract

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We learn: "is this service a good fit for us?" Contract

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Frequent failures may reveal differing priorities Contract

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The maintainer learns: "are people using our service as we expect (or desire)?" Contract

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Maybe this isn't the best service for them Contract

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Maybe this isn't the best service period. Contract ,

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Contract

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Written just like consumption tests Contract

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Committed into the repo of the depended-on service Contract

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Maintainers can lower barrier of entry by providing conveniences Contract

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Contract

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Not a replacement for human interaction Contract

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! ! ! ! ! !! Contract

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! ! ! ! ! !! Contract

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! ! ! ! ! !! Contract

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+ - router web app #1 web app #2 walrus data panda data cage control service

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+ - router walrus data panda data web front- end web back- end web app #1 cage control service

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+ - walrus data web backend panda data router Feed Zoo Animals Build Feed Plan Provide Meal Fetch Schedule Plan Meal Animal Adapter Compute Portions cage control service Release Food Cage Adapter

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+ - provides_meal.rb class ProvidesMeal def initialize... ! def provide(plan) @releases_food.release( @computes_portion.compute(plan) ) end end

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What about TDD? zxc ei

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"What's the point?" eq rf

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"We already have lots of tests!" xc fe

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So far, no feedback about code's design ei kt

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You already have a definition for "unit" test eq xc

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I wrote about this a few months ago xi x

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I wrote about this a few months ago xi x (just Google "tdd failure")

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No content

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It even elicited a response from Uncle Bob! qw rf

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I will refute his arguments and utterly destroy his conclusions. And then, once I'm done salting the ground where he used to live, ...l tell you why I completely agree with him. - Uncle Bob asdz ty

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I will refute his arguments and utterly destroy his conclusions. And then, once I'm done salting the ground where he used to live, I'll tell you why I completely agree with him. - Uncle Bob asdz ty

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There's no "one true TDD" iz rgr

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The principal value of TDD in this model is discovery vj sdf

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Discovery of tiny, boring, consistent units that break big, scary problems down into small, manageable ones ri gh

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Discovery

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The first caller of a new method Discovery

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Concerned primarily with inputs and output (or side effect) Discovery

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Also concerned with basic code design details Discovery

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Inputs & Outcome Discovery Feed Zoo Animals

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Inputs & Outcome Discovery Feed Zoo Animals (walrus, cheese)

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Inputs & Outcome Discovery Feed Zoo Animals (walrus, cheese) Walrus has cheese

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Discovery Now what?!

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Discovery describe FeedsAnimals do end

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Discovery describe FeedsAnimals do describe "#feed" do end end

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Discovery describe FeedsAnimals do describe "#feed" do expect(my_face).to look_like(ಠ_ಠ) end end

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Discovery Feed Zoo Animals Code by wishful thinking!

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Discovery Build Feed Plan Provide Meal Feed Zoo Animals Code by wishful thinking!

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Discovery The test is our sounding board Build Feed Plan Provide Meal Feed Zoo Animals

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Discovery describe FeedsAnimals do ! ! ! end

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Discovery describe FeedsAnimals do Given(:builds_feed_plan) { gimme(BuildsFeedPlan) } ! ! end

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Discovery describe FeedsAnimals do Given(:builds_feed_plan) { gimme(BuildsFeedPlan) } Given(:provides_meal) { gimme(ProvidesMeal) } ! ! end

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Discovery describe FeedsAnimals do Given(:builds_feed_plan) { gimme(BuildsFeedPlan) } Given(:provides_meal) { gimme(ProvidesMeal) } ! subject { FeedsAnimals.new(builds_feed_plan, provides_meal) } ! end

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Discovery describe FeedsAnimals do Given(:builds_feed_plan) { gimme(BuildsFeedPlan) } Given(:provides_meal) { gimme(ProvidesMeal) } ! subject { FeedsAnimals.new(builds_feed_plan, provides_meal) } ! describe "#feed" do end end

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Discovery describe FeedsAnimals do Given(:builds_feed_plan) { gimme(BuildsFeedPlan) } Given(:provides_meal) { gimme(ProvidesMeal) } ! subject { FeedsAnimals.new(builds_feed_plan, provides_meal) } ! describe "#feed" do When(:result) { subject.feed(:walrus, :cheese) } end end

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Discovery describe FeedsAnimals do Given(:builds_feed_plan) { gimme(BuildsFeedPlan) } Given(:provides_meal) { gimme(ProvidesMeal) } ! subject { FeedsAnimals.new(builds_feed_plan, provides_meal) } ! describe "#feed" do When(:result) { subject.feed(:walrus, :cheese) } Then { verify(provides_meal).provide(:cheese, :plan) } end end

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Discovery describe FeedsAnimals do Given(:builds_feed_plan) { gimme(BuildsFeedPlan) } Given(:provides_meal) { gimme(ProvidesMeal) } ! subject { FeedsAnimals.new(builds_feed_plan, provides_meal) } ! describe "#feed" do Given { give(builds_feed_plan).build(:walrus) {:plan}} When(:result) { subject.feed(:walrus, :cheese) } Then { verify(provides_meal).provide(:cheese, :plan) } end end

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Discovery describe FeedsAnimals do Given(:builds_feed_plan) { gimme(BuildsFeedPlan) } Given(:provides_meal) { gimme(ProvidesMeal) } ! subject { FeedsAnimals.new(builds_feed_plan, provides_meal) } ! describe "#feed" do Given { give(builds_feed_plan).build(:walrus) {:plan}} When(:result) { subject.feed(:walrus, :cheese) } Then { verify(provides_meal).provide(:cheese, :plan) } end end

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Discovery Now I have two problems! Build Feed Plan Provide Meal

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Discovery Now I have two problems! Build Feed Plan Provide Meal

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Discovery

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Correct behavior of logical leaf nodes Discovery

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(a.k.a. pure, first- order functions) Discovery

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Discovery Feed Zoo Animals Build Feed Plan Provide Meal

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal Build Feed Plan Provide Meal

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal Compute Portions Release Food Build Feed Plan Provide Meal

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal Compute Portions Release Food Build Feed Plan Provide Meal

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal ✔️ Compute Portions Release Food Build Feed Plan Provide Meal

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal ✔️ Compute Portions Release Food ✔️ Build Feed Plan Provide Meal

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal ✔️ Compute Portions Release Food ✔️ Build Feed Plan Provide Meal

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal ✔️ Compute Portions Release Food ✔️ Build Feed Plan Provide Meal

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Discovery

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Small things Discovery

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Small things Discovery (Free SRP!)

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Separation of Roles Discovery

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal Compute Portions Release Food Build Feed Plan Provide Meal

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal Compute Portions Release Food Build Feed Plan Provide Meal Command

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal Compute Portions Release Food Build Feed Plan Provide Meal Command Query

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal Compute Portions Release Food Build Feed Plan Provide Meal Command Query Command

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal Compute Portions Release Food Build Feed Plan Provide Meal Command Query Query Command

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal Compute Portions Release Food Build Feed Plan Provide Meal Command Query Query Logic Command

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal Compute Portions Release Food Build Feed Plan Provide Meal Command Query Query Logic Logic Command

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Discovery Feed Zoo Animals Fetch Schedule Plan Meal Compute Portions Release Food Build Feed Plan Provide Meal Command Query Query Logic Logic Command Command

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Discovery

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Command & Query tests discover dependencies with test doubles Discovery

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Discovery Logic tests discover implementation by usage

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Discovery (i.e. no test doubles) Logic tests discover implementation by usage

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Commands and Queries contain very little logic Discovery

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Pain is good! Discovery

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Discovery

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Discovery tests yield small, disposable units Discovery

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Discovery tests yield small, disposable units Discovery ...so don't be afraid to throw them away!

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If requirements change, trash a minimal sub-tree of units and drive out a new solution Discovery

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Re-use is overrated Discovery

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Extract refactors are a smell Discovery

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Frameworks will fight you! Discovery

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Frameworks & TDD try to solve the same problems Discovery

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Frameworks provide an orderly structure Discovery

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TDD is an approach for discovering an orderly structure Discovery

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Discovery testing is at odds with most app frameworks Discovery

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! ! ! ! ! !! Discovery

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! ! ! ! ! !! Discovery

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! ! ! ! ! !! Discovery

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+ - provides_meal.rb class ProvidesMeal def initialize... ! def provide(plan) @releases_food.release( @computes_portion.compute(plan) ) end end

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+ - walrus data web backend panda data router Feed Zoo Animals Build Feed Plan Provide Meal Fetch Schedule Plan Meal Animal Adapter Compute Portions cage control service Release Food Cage Adapter

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"Wow, that's a lot of !" zxc tg mock objects

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"Wow, that's a lot of !" fake stuff zxc tg

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"Wow, that's a lot of !" test doubles zxc tg

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"Aren't those many test doubles a pain?" ad er

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They can be! asd xc

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Note: only use doubles when testing collaborators g rg

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Note: better test double libraries are better gr cz

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kdasd fk Discovery tests try to improve dependencies' APIs

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kg er But we can't change 3rd party APIs

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er zxc Mocking what you don't own leads to useless pain

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Wrap 3rd party API calls in adapters that you do own uc vt

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Wrap 3rd party API calls in adapters that you do own uc vt (And mock those adapters instead)

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Typically, adapters shouldn't need tests zx bt

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Most tests exercise features that make use 3rd party APIs jd hn

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It sometimes make sense to test code we don't own separately jd hn

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When you want to respond to 3rd party failures differently, write Adapter tests jd hn

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Adapter

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Your application, pondering its relationship with a 3rd party API Adapter

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Exercises your adapter API under realistic-enough circumstances Adapter

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Adapter

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Adapter Tests of libraries warn of unsafe upgrades

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Adapter Tests of network services warn of outages & breaking changes

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Adapter

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Adapters (& tests) specify how you depend on a thing Adapter

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Establishes boundaries, prevents 3rd party API references from seeping throughout your app Adapter

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Drastically reduces the cost of replacing dependencies later Adapter

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Adapter

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Only test adapters with good cause Adapter

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"Don't test the framework." Adapter

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Adapter

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Adapter test suites of network code can be tricky to run in CI Adapter

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It's easier to test 3rd party services from your SAFE suite Adapter

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All adapter tests are likely to be slow in ways outside your control Adapter

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! ! ! ! ! !! Adapter

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! ! ! ! ! !! Adapter

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! ! ! ! ! !! Adapter

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And that's just way to break up your test suite asd

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And that's just way to break up your test suite asd

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My name is Justin Searls Please tweet me @searls & Say [email protected]

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Like everyone, we're hiring! Just [email protected]

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Please say hello if your team could use our team's help #

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Quotation Marks designed by Horacio Bella from the thenounproject.com ! Happy designed by Michael Hourigan from the thenounproject.com ! Tired designed by Aha-Soft from the thenounproject.com ! Indifference designed by Paul F. from the thenounproject.com ! Mad designed by Aha-Soft from the thenounproject.com ! Sad designed by Simple Icons from the thenounproject.com ! Marker designed by Jeff Seevers from the thenounproject.com ! Database designed by Grant Fisher from the thenounproject.com ! Cloud designed by Thomas Hirter from the thenounproject.com ! Safety Net designed by irene hoffman from the thenounproject.com ! Light Bulb designed by Olivier Guin from the thenounproject.com ! Scale designed by Stephanie Wauters from the thenounproject.com ! Warning designed by Lorena Salagre from the thenounproject.com ! Reload designed by Mateo Zlatar from the thenounproject.com Noun project attribution