Dont Mock Yourself Out David Chelimsky Articulated Man, Inc - PowerPoint PPT Presentation

describe Statement do it "uses the customer name in the header" do customer = stub("customer") customer.stub(:name).and_return('Joe Customer') statement = Statement.new(customer) statement.header.should == "Statement for Joe Customer" end end message expectation class Statement def header "Statement for #{@customer.name}" end end

describe Statement do it "uses the customer name in the header" do customer = stub("customer") customer.stub(:name).and_return('Joe Customer') statement = Statement.new(customer) statement.header.should == "Statement for Joe Customer" end end bound to implementation class Statement def header "Statement for #{@customer.name}" end end

stubs are often used like mocks

mocks are often used like stubs

we verify stubs by checking state after an action

we tell mocks to verify interactions

sometimes stubs just make the system run

when are method stubs helpful?

isolation from non-determinism

random values

random values class BoardTest < MiniTest::Unit::TestCase def test_allows_move_to_last_square board = Board.new( :squares => 50, :die => MiniTest::Mock.new.expect('roll', 2) ) piece = Piece.new board.place(piece, 48) board.move(piece) assert board.squares[48].contains?(piece) end end

time describe Event do it "is not happening before the start time" do now = Time.now start = now + 1 Time.stub(:now).and_return now event = Event.new(:start => start) event.should_not be_happening end end

isolation from external dependencies

network access Database Interface Database Subject Network Internets Interface

network access def test_successful_purchase_sends_shipping_message ActiveMerchant::Billing::Base.mode = :test gateway = ActiveMerchant::Billing::TrustCommerceGateway.new( :login => 'TestMerchant', :password => 'password' ) item = stub() messenger = mock() messenger.expects(:ship).with(item) purchase = Purchase.new(gateway, item, credit_card, messenger) purchase.finalize end

network access Stub Database Code Subject Example Stub Network

network access def test_successful_purchase_sends_shipping_message gateway = stub() gateway.stubs(:authorize).returns( ActiveMerchant::Billing::Response.new(true, "ignore") ) item = stub() messenger = mock() messenger.expects(:ship).with(item) purchase = Purchase.new(gateway, item, credit_card, messenger) purchase.finalize end

polymorphic collaborators

strategies describe Employee do it "delegates pay() to payment strategy" do payment_strategy = mock() employee = Employee.new(payment_strategy) payment_strategy.expects(:pay) employee.pay end end

mixins/plugins describe AgeIdentifiable do describe "#can_vote?" do it "raises if including does not respond to birthdate" do object = Object.new object.extend AgeIdentifiable expect { object.can_vote? }.to raise_error( /must supply a birthdate/ ) end it "returns true if birthdate == 18 years ago" do object = Object.new stub(object).birthdate {18.years.ago.to_date} object.extend AgeIdentifiable object.can_vote?.should be(true) end end end

when are message expectations helpful?

side effects describe Statement do it "logs a message when printed" do customer = stub("customer") customer.stub(:name).and_return('Joe Customer') logger = mock("logger") statement = Statement.new(customer, logger) logger.should_receive(:log).with(/Joe Customer/) statement.print end end

caching describe ZipCode do it "should only validate once" do validator = mock() zipcode = ZipCode.new("02134", validator) validator.should_receive(:valid?).with("02134").once. and_return(true) zipcode.valid? zipcode.valid? end end

interface discovery describe "thing I'm working on" do it "does something with some assistance" do thing_i_need = mock() thing_i_am_working_on = ThingIAmWorkingOn.new(thing_i_need) thing_i_need.should_receive(:help_me).and_return('what I need') thing_i_am_working_on.do_something_complicated end end

isolation testing

specifying/testing individual objects in isolation

good fit with lots of little objects

all of these concepts apply to the non-rails specific parts of our rails apps

isolation testing the rails-specific parts of our applicationss

V M C

View Controller Model

Browser Router View Controller Model Database

rails testing ๏ unit tests ๏ functional tests ๏ integration tests

rails unit tests ๏ model classes (repositories) ๏ model objects ๏ database

rails functional tests ๏ model classes (repositories) ๏ model objects ๏ database ๏ views ๏ controllers

rails functional tests ๏ model classes (repositories) ๏ model objects ๏ database ๏ views ๏ controllers

rails functional tests ๏ model classes (repositories) ๏ model objects ๏ database !DRY ๏ views ๏ controllers

rails integration tests ๏ model classes (repositories) ๏ model objects ๏ database ๏ views ๏ controllers ๏ routing/sessions

rails integration tests ๏ model classes (repositories) ๏ model objects ๏ database !DRY ๏ views ๏ controllers ๏ routing/sessions

the BDD approach

inherited from XP

customer specs developer specs

rails integration tests + webrat shoulda, context, micronaut, etc

customer specs are implemented as end to end tests

developer specs are implemented as isolation tests

mocking and stubbing with rails

partials in view specs describe "/registrations/new.html.erb" do before(:each) do template.stub(:render).with(:partial => anything) end it "renders the registration navigation" do template.should_receive(:render).with(:partial => 'nav') render end it "renders the registration form " do template.should_receive(:render).with(:partial => 'form') render end end

conditional branches in controller specs describe "POST create" do describe "with valid attributes" do it "redirects to list of registrations" do registration = stub_model(Registration) Registration.stub(:new).and_return(registration) registration.stub(:save!).and_return(true) post 'create' response.should redirect_to(registrations_path) end end end

conditional branches in controller specs describe "POST create" do describe "with invalid attributes" do it "re-renders the new form" do registration = stub_model(Registration) Registration.stub(:new).and_return(registration) registration.stub(:save!).and_raise( ActiveRecord::RecordInvalid.new(registration)) post 'create' response.should render_template('new') end end end

conditional branches in controller specs describe "POST create" do describe "with invalid attributes" do it "assigns the registration" do registration = stub_model(Registration) Registration.stub(:new).and_return(registration) registration.stub(:save!).and_raise( ActiveRecord::RecordInvalid.new(registration)) post 'create' assigns[:registration].should equal(registration) end end end

shave a few lines but leave a little stubble http://github.com/dchelimsky/stubble

stubble describe "POST create" do describe "with valid attributes" do it "redirects to list of registrations" do stubbing(Registration) do post 'create' response.should redirect_to(registrations_path) end end end end

stubble describe "POST create" do describe "with invalid attributes" do it "re-renders the new form" do stubbing(Registration, :as => :invalid) do post 'create' response.should render_template('new') end end it "assigns the registration" do stubbing(Registration, :as => :invalid) do |registration| post 'create' assigns[:registration].should equal(registration) end end end end

chains describe UsersController do it "GET 'best_friend'" do member = stub_model(User) friends = stub() friend = stub_model(User) User.stub(:find).and_return(member) member.stub(:friends).and_return(friends) friends.stub(:favorite).and_return(friend) get :best_friend, :id => '37' assigns[:friend].should equal(friend) end end

chains describe UsersController do it "GET 'best_friend'" do friend = stub_model(User) User.stub_chain(:find, :friends, :favorite). and_return(friend) get :best_friend, :id => '37' assigns[:friend].should equal(friend) end end