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better code through boring(er) tests BETSY HAIBEL @betsythemuffin

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everyone values testing @betsythemuffin

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TYPE A QUOTE HERE. @betsythemuffin

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literally no one loves testing all the time ‣not even me ‣it’s ok to admit it ‣the testing police are not coming for you @betsythemuffin

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GROUNDWORK WHAT WE’RE GONNA DO ABOUT THAT TODAY ▸ learn why we hate our tests :( ▸ learn why we fight about tests :( ▸ learn about ways we accidentally make our tests worse :( ▸ learn how to fix those! ▸ learn how to make our app code better at the same time! @betsythemuffin

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GROUNDWORK WHAT WE’RE GONNA DO ABOUT THAT TODAY UNDERLYING REASONS @betsythemuffin

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GROUNDWORK WHAT WE’RE GONNA DO ABOUT THAT TODAY UNDERLYING REASONS SPECIFIC EXAMPLES @betsythemuffin

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GROUNDWORK WHAT WE’RE GONNA DO ABOUT THAT TODAY UNDERLYING REASONS SPECIFIC EXAMPLES @betsythemuffin

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GROUNDWORK WHAT WE’RE GONNA DO ABOUT THAT TODAY UNDERLYING REASONS SPECIFIC EXAMPLES @betsythemuffin

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GROUNDWORK WHAT WE’RE GONNA DO ABOUT THAT TODAY UNDERLYING REASONS SPECIFIC EXAMPLES @betsythemuffin

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tests are code and are therefore terrible UNDERLYING REASONS @betsythemuffin

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you write your tests with the same imperfect knowledge as you write all your code UNDERLYING REASONS @betsythemuffin

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WHY DON’T YOU TRY LISTENING TO YOUR TESTS? some jerk who likes TDD too much THIS IS THE THING THAT ALWAYS HAPPENS. CRIKEY. UNDERLYING REASONS @betsythemuffin

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1. TESTS YOU HATE 2. ??? 3. CODE YOU DON’T HATE some jerk who likes TDD too much WE TRANSLATE, WITHOUT EXCESSIVE KINDNESS UNDERLYING REASONS @betsythemuffin

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UGH I THINK WE CAN FIX THIS IF WE JUST TRY. I PROMISE. a TDDer who is not communicating well yet WE TRANSLATE, WITH SOMEWHAT MORE EMPATHY @betsythemuffin

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some notes before we get started properly ‣bad code happens ‣bad tests happen ‣this is fine UNDERLYING REASONS @betsythemuffin

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code is terrible because the world is complex UNDERLYING REASONS @betsythemuffin

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we invented esoteric testing techniques for good reasons UNDERLYING REASONS @betsythemuffin

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everything I am about to show you I have done in production especially the parts I say are bad UNDERLYING REASONS @betsythemuffin

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TESTING PRIVATE METHODS @betsythemuffin

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@book.send(:dogear) # a private method! TESTING PRIVATE METHODS - THE PROBLEM @betsythemuffin

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WHY DO PEOPLE TEST PRIVATE METHODS? ▸ indirect results ▸ expensive to test via public interface ▸ weird side effects elsewhere TESTING PRIVATE METHODS - THE PROBLEM @betsythemuffin

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ALTERNATIVES TO TESTING PRIVATE METHODS ▸ make the method public ▸ build more introspection logic ▸ extract a simple class TESTING PRIVATE METHODS - ALTERNATIVES @betsythemuffin

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def dogear DogearMaker.new(self).call end class DogearMaker def initialize(target) @target = target end def call # stuff end end TESTING PRIVATE METHODS - EXTRACT SIMPLE CLASS @betsythemuffin

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it’s ok to fix things later TESTING PRIVATE METHODS - DEFER THE DECISION @betsythemuffin

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DUPLICATE TESTS @betsythemuffin

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class ClientTest < Minitest::Test def test_mobile_phones @client.phone_number = MOBILE_PHONE assert @client.mobile_phone? end def test_landline_phones @client.phone_number = LANDLINE_PHONE assert [email protected]_phone? end end DUPLICATE TESTS - THE PROBLEM @betsythemuffin

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def test_mobile_phones @client.phone_number = MOBILE_PHONE assert @client.mobile_phone? end it ‘can have a mobile phone‘ do subject.phone_number = MOBILE_PHONE expect(subject.mobile_phone?).to be(true) end DUPLICATE TESTS - THE PROBLEM @betsythemuffin

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class ClientTest < Minitest::Test def test_mobile_phones @client.phone_number = MOBILE_PHONE assert @client.mobile_phone? end def test_landline_phones @client.phone_number = LANDLINE_PHONE assert [email protected]_phone? end end DUPLICATE TESTS - THE PROBLEM @betsythemuffin

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class DonorrTest < Minitest::Test def test_mobile_phones @donorr.phone_number = MOBILE_PHONE assert @donorr.mobile_phone? end def test_landline_phones @donorr.phone_number = LANDLINE_PHONE assert [email protected]_phone? end end DUPLICATE TESTS - THE PROBLEM @betsythemuffin

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module HasPhoneNumberTest def test_mobile_phones @subjec.phone_number = MOBILE_PHONE assert @subjec.mobile_phone? end def test_landline_phones @subjec.phone_number = LANDLINE_PHONE assert [email protected]_phone? end end DUPLICATE TESTS - THE SHARED EXAMPLE GROUP SMELL @betsythemuffin

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class ClientTest < Minitest::Test include HasPhoneNumberTest end class CustomerTest < Minitest::Test include HasPhoneNumberTest end DUPLICATE TESTS - THE SHARED EXAMPLE GROUP SMELL @betsythemuffin

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class Client include HasPhoneNumber end class Customer include HasPhoneNumber end DUPLICATE TESTS - THE SHARED EXAMPLE GROUP SMELL @betsythemuffin

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this locks us into assumptions DUPLICATE TESTS - THE SHARED EXAMPLE GROUP SMELL @betsythemuffin

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class HasPhoneNumberTest < Minitest::Test class HasPhone include HasPhoneNumber end def test_landline_phones @has_phone = HasPhone.new @has_phone.phone_number = LANDLINE_PHONE assert !@has_phone.mobile_phone? end end DUPLICATE TESTS - THE DIRECT MODULE TEST SMELL @betsythemuffin

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class PhoneNumber attr_accessor :value def mobile_phone? # complicated lookup logic end end DUPLICATE TESTS - THE EXTRACT CLASS FIX @betsythemuffin

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test duplication sometimes means functional duplication DUPLICATE TESTS - THE KEY IDEA @betsythemuffin

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INVENTING THE UNIVERSE @betsythemuffin

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class PieTest < Minitest::Test def test_pie_tastes_good @universe.invent @apple_seed = AppleSeed.new @orchard = Orchard.new @orchard.plant(@apple_seed) @orchard.water! let_much_time_pass @apple_tree = Orchard.find_tree_from(@apple_seed) # etc assert @pie.filling_set_properly? assert @pie.cinnamon_level > 6 assert @pie.super_flaky_crust? end end INVENTING THE UNIVERSE - THE PROBLEM @betsythemuffin

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class PieTest < Minitest::Test def test_pie_tastes_good # many other lines assert @pie.filling_set_properly? assert @pie.cinnamon_level > 6 assert @pie.super_flaky_crust? end end INVENTING THE UNIVERSE - THE PROBLEM @betsythemuffin

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first, pretend this isn’t terrible. INVENTING THE UNIVERSE - THE PREMATURE FIX SMELL @betsythemuffin

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class PieTest < Minitest::Test def test_pie_tastes_good @universe.invent @apple_seed = AppleSeed.new @orchard = Orchard.new @orchard.plant(@apple_seed) @orchard.water! let_much_time_pass @apple_tree = Orchard.find_tree_from(@apple_seed) # etc assert @pie.filling_set_properly? assert @pie.cinnamon_level > 6 assert @pie.super_flaky_crust? end end INVENTING THE UNIVERSE - THE PREMATURE FIX SMELL @betsythemuffin

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your tests use your application’s assumptions (unless you try very hard) INVENTING THE UNIVERSE - THE PREMATURE FIX SMELL @betsythemuffin

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wait until you have multiple tests INVENTING THE UNIVERSE - THE PREMATURE FIX SMELL @betsythemuffin

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shared contexts INVENTING THE UNIVERSE - SHARED CONTEXT SMELL @betsythemuffin

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class PieTest < Minitest::Test include ReliesOnUniverseExisting def setup invent_universe end end INVENTING THE UNIVERSE - SHARED CONTEXT SMELL @betsythemuffin

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WHAT ARE SHARED CONTEXTS GOOD FOR? ▸ database setup ▸ inventing the universe INVENTING THE UNIVERSE - SHARED CONTEXT SMELL @betsythemuffin

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WHAT DO SHARED CONTEXTS HIDE FROM US? ▸ dependencies ▸ (but that’s not the whole story) INVENTING THE UNIVERSE - SHARED CONTEXT SMELL @betsythemuffin

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factory_girl INVENTING THE UNIVERSE - FACTORY_GIRL SMELL @betsythemuffin

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FactoryGirl.create(:pie) FactoryGirl.create(:filling) # omg they look the same! INVENTING THE UNIVERSE - FACTORY_GIRL SMELL @betsythemuffin

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saying “dependencies” is cheating INVENTING THE UNIVERSE - FACTORY_GIRL SMELL @betsythemuffin

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saying “dependencies” is cheating INVENTING THE UNIVERSE - FACTORY_GIRL SMELL @betsythemuffin

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“dependencies” just means “code you’re not looking at” INVENTING THE UNIVERSE - FACTORY_GIRL SMELL @betsythemuffin

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just don’t hide domain logic INVENTING THE UNIVERSE - FACTORY_GIRL SMELL @betsythemuffin

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# constructor: Pie.new(filling: PumpkinPieFilling.new) INVENTING THE UNIVERSE - THE PLAIN FACTORY FIX @betsythemuffin

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# constructor: Pie.new(filling: PumpkinPieFilling.new) # factory method on class: Pie.bake_with(PumpkinPieFilling.new) INVENTING THE UNIVERSE - THE PLAIN FACTORY FIX @betsythemuffin

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# constructor: Pie.new(filling: PumpkinPieFilling.new) # factory method on class: Pie.bake_with(PumpkinPieFilling.new) # java-style factory class factory = PieFactory.new factory.add_filling(PumpkinPieFilling.new) @pie = factory.bake INVENTING THE UNIVERSE - THE PLAIN FACTORY FIX @betsythemuffin

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Business logic is too important to delegate to framework magic INVENTING THE UNIVERSE - THE PLAIN FACTORY FIX @betsythemuffin

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class PieTest < Minitest::Test def test_pie_tastes_good @universe.invent @apple_seed = AppleSeed.new @orchard = Orchard.new @orchard.plant(@apple_seed) @orchard.water! let_much_time_pass @apple_tree = Orchard.find_tree_from(@apple_seed) # etc assert @pie.filling_set_properly? assert @pie.cinnamon_level > 6 assert @pie.super_flaky_crust? end end INVENTING THE UNIVERSE - THE PLAIN FACTORY FIX @betsythemuffin

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@universe.invent @apple_seed = AppleSeed.new @orchard = Orchard.new @orchard.plant(@apple_seed) @orchard.water! let_much_time_pass @apple_tree = Orchard.find_tree_from(@apple_seed) # etc assert @pie.filling_set_properly? assert @pie.cinnamon_level > 6 assert @pie.super_flaky_crust? INVENTING THE UNIVERSE - THE PLAIN FACTORY FIX @orchard = Universe.with_orchard(Apple) @pie = Pie.from(@orchard.fruit) assert @pie.filling_set_properly? assert @pie.cinnamon_level > 6 assert @pie.super_flaky_crust?

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INVENTING THE UNIVERSE - THE PLAIN FACTORY FIX class PieTest < Minitest::Test def test_pie_tastes_good @orchard = Universe.with_orchard(Apple) @pie = Pie.from(@orchard.fruit) assert @pie.filling_set_properly? assert @pie.cinnamon_level > 6 assert @pie.super_flaky_crust? end end @betsythemuffin

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A MAGIC TRICK @betsythemuffin

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A MAGIC TRICK @betsythemuffin

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this is subjective A MAGIC TRICK @betsythemuffin

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how do we define boring? A MAGIC TRICK @betsythemuffin

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i think: code that minimizes assumptions is boring A MAGIC TRICK @betsythemuffin

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application code influences test code test code influences application code A MAGIC TRICK @betsythemuffin

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1. TESTS YOU DON’T HATE 2. REFACTORING 3. CODE YOU DON’T HATE all “listening to your tests” means A CONCLUSION @betsythemuffin

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SHAMELESS PROMOTION TIME BETSY HAIBEL ▸ @betsythemuffin ▸ betsyhaibel.com ▸ github.com/bhaibel ▸ roostify.com/jobs @betsythemuffin

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QUESTIONS? you, maybe TEXT @betsythemuffin