RSpec and Testing Best Practices

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RSpec and Testing Best Practices @samnangchhun

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Review Quick

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RSpec.describe "HelloMessage" do context "when passing name" do it "returns hello message with passing name" do result = HelloMessage.new("Samnang").result expect(result).to eq("Hello Samnang!") end end context "without passing name" do it "returns the default of hello message" do result = HelloMessage.new.result expect(result).to eq("Hello World!") end end end

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class HelloMessage def initialize(name = nil) @name = name end def result if @name "Hello %s!" % @name else "Hello World!" end end end

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class HelloMessage DEFAULT_MESSAGE = "World" def initialize(name = DEFAULT_MESSAGE) @name = name end def result "Hello %s!" % @name end end

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Running Specs

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--format https://github.com/thekompanee/fuubar https://github.com/grosser/rspec-instafail

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--tag

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--profile

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--fail-fast

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.rspec 45RGETGCFUEQOOCPFNKPGEQPHKIWTCVKQPQRVKQPUHTQOHKNGUKPVJTGGFKHHGTGPVNQECVKQPU • .QECN ./.rspec-local • 2TQLGEV ./.rspec • )NQDCN ~/.rspec

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skip RSpec.describe "A feature" do xit "skip with xit" do end skip "skip with inline method call" do end it "skip with tag skip", skip: "give a reason" do end it "skip with method call" do skip("give a reason") end end

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pending RSpec.describe "A feature" do it "pending with tag pending", pending: 'give a reason' do end pending "pending with inline method call" do end it "pending with method call" do pending("give a reason") end end

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Running specs in Editors

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Fundamental RSepc

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let ō .C\[GXCNWCVKQP OGOQK\CVKQP ō 4GETGCVGFGCEJGZCORNG RSpec.describe User do describe "#locked?" do let(:user) { User.new(cards: cards) } context "when user no chards" do let(:cards) { [] } # examples end end end

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subject ō .C\[GXCNWCVKQP OGOQK\CVKQP ō +ORTQXG4GCFCDKNKV[ ō &4; RSpec.describe User, type: :model do describe "validations" do subject { build(:user) } it { is_expected.to validate_presence_of(:email) } it { is_expected.to validate_uniqueness_of(:email) } it { is_expected.to validate_length_of(:username).is_at_least(3) } it { is_expected.to validate_uniqueness_of(:username) } end end

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Build in matchers # Object equivalence expect(actual).to eq(expected) # Comparisons expect(actual).to be > expected expect(actual).to match(/expression/) expect(actual).to be_within(delta).of(expected) # Types/classes/response expect(actual).to be_instance_of(expected) expect(actual).to be_kind_of(expected) expect(actual).to respond_to(expected) # Expecting errors expect { ... }.to raise_error expect { ... }.to raise_error(ErrorClass) https://www.relishapp.com/rspec/rspec-expectations/docs/built-in-matchers

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Custom matchers https://www.relishapp.com/rspec/rspec-expectations/docs/custom-matchers RSpec::Matchers.define :be_a_multiple_of do |expected| match do |actual| actual % expected == 0 end end RSpec.describe 9 do it { is_expected.to be_a_multiple_of(3) } end RSpec.describe 9 do it { is_expected.not_to be_a_multiple_of(4) } end

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Composing matchers describe BackgroundWorker do it 'puts enqueued jobs onto the queue in order' do worker = BackgroundWorker.new worker.enqueue(:klass => "Class1", :id => 37) worker.enqueue(:klass => "Class2", :id => 42) expect(worker.queue).to match [ a_hash_including(:klass => "Class1", :id => 37), a_hash_including(:klass => "Class2", :id => 42) ] end end

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Compound Expectations class StopLight def color %w[ green yellow red ].shuffle.first end end RSpec.describe StopLight, "#color" do let(:light) { StopLight.new } it "is green, yellow or red" do expect(light.color).to eq("green").or eq("yellow").or eq("red") end it "passes when using boolean OR | alias" do expect(light.color).to eq("green") | eq("yellow") | eq("red") end end

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Test Doubles RSepc

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Mock Stub Fake Spy Test Double

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Test Double 6GUVFQWDNGKUCIGPGTKEVGTOHQTCP[QDLGEVVJCVUVCPFUKPHQT CTGCNQDLGEVFWTKPICVGUV VJKPMUVWPVFQWDNGŉ Ń45RGE/QEMFQEWOGPVCVKQP https://www.relishapp.com/rspec/rspec-mocks/docs/basics/test-doubles

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Allowing messages RSpec.describe UsersController do describe "GET :show" do it "assigns :user" do user = double(:user) allow(User).to receive(:find).with("1").and_return(user) get :show, id: 1 expect(assigns[:user]).to eq(user) end end end

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Expecting messages RSpec.describe MonthlySubscriptionCharger do context "when user has active subscription" do it "charges user with their plan" do user = double(:user, active_subscription?: true) creditcard_charger = double(:creditcard_charger) expect(creditcard_charger).to receive(:charge).with(user) monthly_charger = MonthlySubscriptionCharger.new(user, creditcard_charger) monthly_charger.call end end end

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Expecting messages class MonthlySubscriptionCharger def initialize(user, creditcard_charger) @user = user @creditcard_charger = creditcard_charger end def call if @user.active_subscription? @creditcard_charger.charge(@user) end end end

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Spies RSpec.describe MonthlySubscriptionCharger do context "when user has active subscription" do it "charges user with their plan" do user = double(:user, active_subscription?: true) creditcard_charger = double(:creditcard_charger, charge: true) monthly_charger = MonthlySubscriptionCharger.new(user, creditcard_charger) monthly_charger.call expect(creditcard_charger).to have_received(:charge).with(user) end end end

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Spies RSpec.describe MonthlySubscriptionCharger do context "when user has active subscription" do it "charges user with their plan" do user = double(:user, active_subscription?: true) creditcard_charger = double(:creditcard_charger).as_null_object monthly_charger = MonthlySubscriptionCharger.new(user, creditcard_charger) monthly_charger.call expect(creditcard_charger).to have_received(:charge).with(user) end end end

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Spies RSpec.describe MonthlySubscriptionCharger do context "when user has active subscription" do it "charges user with their plan" do user = double(:user, active_subscription?: true) creditcard_charger = spy(:creditcard_charger) monthly_charger = MonthlySubscriptionCharger.new(user, creditcard_charger) monthly_charger.call expect(creditcard_charger).to have_received(:charge).with(user) end end end

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Testing Best Practices

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How to describe your behaviors RSpec.feature "Widget management", :type => :feature do scenario "User creates a new widget" do visit "/widgets/new" fill_in "Name", :with => "My Widget" click_button "Create Widget" expect(page).to have_text("Widget was successfully created.") end end

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How to describe your behaviors RSpec.describe User do describe "#full_name" do it "return full name of user" do user = User.new(first_name: 'Samnang', last_name: 'Chhun') result = user.full_name expect(result).to eq('Samnang Chhun') end end end

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Use contexts RSpec.describe User do describe "#full_name" do context "when user missing first name" do # examples end context "when user has middle name" do # examples end end end

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Four-Phase Test test do setup exercise verify teardown end it "encrypts the password" do user = User.new(password: 'password') user.save expect(user.encrypted_password).not_to be_nil end

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Let’s Not RSpec.describe User do describe "#valid?" do let(:user) { User.new(attributes) } context "when passing valid attributes" do let(:attributes) { { first_name: "Samnang", last_name: "Chhun" } } it "returns true" do expect(user.valid?).to eq(true) end end context "when passing invalid attributes" do let(:attributes) { { first_name: nil, last_name: "Chhun" } } it "returns false" do expect(user.valid?).to eq(false) end end end end

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Let’s Not RSpec.describe User do describe "#valid?" do context "when passing valid attributes" do it "returns true" do user = build_user(first_name: "Samnang", last_name: "Chhun") expect(user.valid?).to eq(true) end end context "when passing invalid attributes" do it "returns false" do user = build_user(first_name: nil, last_name: "Chhun") expect(user.valid?).to eq(false) end end def build_user(attributes) User.new(attributes) end end end

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Define custom matchers RSpec::Matchers.define :have_access_to do |beta_feature| match do |user| FeatureToggle.has_access?(user, beta_feature) end end RSpec.describe User do subject { build_stubbed(:beta_user) } it { is_expected.to have_access_to :mystery_machine } end

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Only one expectation per example RSpec.describe "HelloMessage" do it "returns hello message" do result_passing_name = HelloMessage.new("Samnang").result result_without_passing_name = HelloMessage.new.result expect(result_passing_name).to eq("Hello Samnang!") expect(result_without_passing_name).to eq("Hello World!") end end

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Only one expectation per example RSpec.describe "HelloMessage" do context "when passing name" do it "returns hello message with passing name" do result = HelloMessage.new("Samnang").result expect(result).to eq("Hello Samnang!") end end context "without passing name" do it "returns the default of hello message" do result = HelloMessage.new.result expect(result).to eq("Hello World!") end end end

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Only one expectation per example Only one logical expectation per example

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Avoid touching DB RSpec.describe User do describe "#full_name" do it "return full name of user" do user = FactoryGirl.create(:user, first_name: "Samnang", last_name: "Chhun") expect(user.full_name).to eq("Samnang Chhun") end end end

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Avoid touching DB RSpec.describe User do describe "#full_name" do it "return full name of user" do user = User.new(first_name: “Samnang", last_name: "Chhun") expect(user.full_name).to eq("Samnang Chhun") end end end

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Testing Pyramid http://blog.codeclimate.com/blog/2013/10/09/rails-testing-pyramid/

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Thank you!

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References • https://www.relishapp.com/rspec/ • http://betterspecs.org/ • https://robots.thoughtbot.com/lets-not • https://robots.thoughtbot.com/four-phase-test • https://robots.thoughtbot.com/speed-up-tests-by-selectively-avoiding-factory-girl • http://blog.codeclimate.com/blog/2013/10/09/rails-testing-pyramid/ • http://martinfowler.com/articles/mocksArentStubs.html • https://github.com/thoughtbot/guides/tree/master/best-practices#testing