TDD & SOLID Mike Nicholaides

http://promptworks.com! @promptworks

describe Notifier, "#notify" do let(:message_body) do "Hi @#{notifiable_user1.name} @#{notifiable_user2.name}\ @#{ unnotifiable_user.name }" end ! let(:message) { create(:message, body: message_body) } ! it "FB's the message's mentioned users who prefer to be FB'd" do notifiable_user1 = create(:facebook_connected_user, fb_me_on_mention: true) notifiable_user2 = create(:facebook_connected_user, fb_me_on_mention: true) unnotifiable_user = create(:facebook_connected_user, fb_me_on_mention: false) ! notifiable_user1.facebook_connection.stub(put_connections: true) notifiable_user2.facebook_connection.stub(put_connections: true) unnotifiable_user.facebook_connection.stub(put_connections: true) ! Notifier.notify(message) ! expected_message = "#{message.author.name} said #{message_body}" ! expect(notifiable_user1.facebook_connection).to have_received(:put_connections).with("me", "feed", message: expected_message) expect(notifiable_user2.facebook_connection).to have_received(:put_connections).with("me", "feed", message: expected_message) expect(unnotifiable_user.facebook_connection).not_to have_received(:put_connections) end ! it "emails the message's mentioned users who prefer to be emailed" do notifiable_user1 = create(:user, email_me_on_mention: true) notifiable_user2 = create(:user, email_me_on_mention: true) unnotifiable_user = create(:user, email_me_on_mention: false) ! MessageMailer.stub(:deliver_message) ! Notifier.notify(message) ! expected(MessageMailer).to have_received(:deliver_message).with(message, [notifiable_user1, notifiable_user2]) end ! it "SMS's the message's mentioned users who prefer to be SMS'd" do notifiable_user1 = create(:sms_user, sms_me_on_mention: true) notifiable_user2 = create(:sms_user, sms_me_on_mention: true) unnotifiable_user = create(:sms_user, sms_me_on_mention: false) ! SMSGateway.stub(:deliver) ! Notifier.notify(message) ! expected_message = "#{message.author.name} said #{message_body}" ! expect(SMSGateway).to have_received(:deliver).with(expected_message, notifiable_user1.sms_number) expect(SMSGateway).to have_received(:deliver).with(expected_message, notifiable_user2.sms_number) end end

class Notifier def self.notify(message) message.mentioned_users. select(&:fb_me_on_mention?). select(&:facebook_connection). each do |user| user.facebook_connection.put_connections( "me", "feed", message: "#{message.author.name} said: #{message.body}" ) end ! email_users = message.mentioned_users. select(&:email_me_on_mention?). select{|u| u.email.present? } MessageMailer.deliver_message(message, email_users) ! message.mentioned_users. select(&:sms_me_on_mention?). select{|u| u.sms_number.present? }. each { |user| SMSGateway.deliver(message, user.sms_number) } end end

Test first != good code

SOLID

Interface Segregation Principle “many client-specific interfaces are better than one general-purpose interface.” ! Robert C. Martin Principles of Object Oriented Design

Dependency Inversion Principle “Depend upon abstractions. Do not depend upon concretions.” ! ! Robert C. Martin, Design Principles and Design Patterns

Depending on a Concretion def save_my_game if game_changed? File.open('game.txt', 'w') do |file| file.print @game_data end end end ! save_my_game

Depending on an Abstraction def save_my_game persistent_store = FileStore.new persistent_store.save(@game_data) if game_changed? end ! save_my_game class FileStore def save(game_data) File.open('game.txt', 'w') do |file| file.print game_data end end end

Dependency Inversion Principle hide concretions behind abstractions

Open/Closed Principle “Software entities … should be open for extension, but closed for modification” ! Bertrand Meyer, Object Oriented Software Construction

Open/Closed Principle • dependencies • collaborators • logic Swappable pieces for

Open/Closed Principle • blocks • inheritance • dependency injection Techniques

Open/Closed Principle def save_my_game(persistent_store) persistent_store.save(@game_data) if game_changed? end ! save_my_game(FileStore.new)

Open/Closed Principle Make entities extendible

Liskov Substitution Principle • use duck typing

Liskov Substitution Principle def save_my_game(persistent_store) persistent_store.save(@game_data) if game_changed? end

Single Responsibility Principle “A class should have one, and only one, reason to change.” ! Robert C. Martin Principles of Object Oriented Design

Single Responsibility Principle • classes should be small • classes should do one thing • we should have lots of classes

SOLID • hide concretions behind abstractions • make entities extendible • use duck typing • classes should do one thing

message.author # => User @JesseKatsopolis ! message.body # => "@DannyTanner, @JoeyGladstone, Watch the hair!" ! message.mentioned_users # => [ User @DannyTanner, User @JoeyGladstone ]

# ... ! if @message.save ! Notifier.notify(@message) ! redirect_to @message else ! # ...

describe Notifier, ".notify" do ! it "emails the message's mentioned users who prefer to be emailed" it "SMS's the message's mentioned users who prefer to be SMS'd" it "FB's the message's mentioned users who prefer to be FB'd" ! end

Details • what it does • what is knows

Responsibilities • email users • SMS users • FB users ! Concretions • the message • the mentioned users • how to determine if someone wants to be emailed • how to determine if someone wants to be SMS'd • how to determine if someone wants to be FB'd


Responsibilities Described it "emails the message's mentioned users who prefer to be emailed" it "SMS's the message's mentioned users who prefer to be SMS'd" it "FB's the message's mentioned users who prefer to be FB'd"

Strained Language It emails the messages' mentioned users who prefer to be emailed.

it "FB's the message's mentioned users who prefer to be FB'd" do ! notifiable_user1 = create(:facebook_connected_user, fb_me_on_mention: true) notifiable_user2 = create(:facebook_connected_user, fb_me_on_mention: true) unnotifiable_user = create(:facebook_connected_user, fb_me_on_mention: false) ! message_body = "Hi @#{notifiable_user1.name} @#{notifiable_user2.name}\ @#{ unnotifiable_user.name }" ! message = create(:message, body: message_body) ! notifiable_user1.facebook_connection.stub(put_connections: true) notifiable_user2.facebook_connection.stub(put_connections: true) unnotifiable_user.facebook_connection.stub(put_connections: true) ! Notifier.notify(message) ! expected_message = "#{message.author.name} said #{message_body}" ! expect(notifiable_user1.facebook_connection). to have_received(:put_connections). with("me", "feed", message: expected_message) ! expect(notifiable_user2.facebook_connection). to have_received(:put_connections). with("me", "feed", message: expected_message) ! expect(unnotifiable_user.facebook_connection). not_to have_received(:put_connections) ! end

too many details == hard to test

describe Notifier, "#notify" do let(:message_body) do "Hi @#{notifiable_user1.name} @#{notifiable_user2.name}\ @#{ unnotifiable_user.name }" end ! let(:message) { create(:message, body: message_body) } ! it "FB's the message's mentioned users who prefer to be FB'd" do notifiable_user1 = create(:facebook_connected_user, fb_me_on_mention: true) notifiable_user2 = create(:facebook_connected_user, fb_me_on_mention: true) unnotifiable_user = create(:facebook_connected_user, fb_me_on_mention: false) ! notifiable_user1.facebook_connection.stub(put_connections: true) notifiable_user2.facebook_connection.stub(put_connections: true) unnotifiable_user.facebook_connection.stub(put_connections: true) ! Notifier.notify(message) ! expected_message = "#{message.author.name} said #{message_body}" ! expect(notifiable_user1.facebook_connection).to have_received(:put_connections).with("me", "feed", message: expected_message) expect(notifiable_user2.facebook_connection).to have_received(:put_connections).with("me", "feed", message: expected_message) expect(unnotifiable_user.facebook_connection).not_to have_received(:put_connections) end ! it "emails the message's mentioned users who prefer to be emailed" do notifiable_user1 = create(:user, email_me_on_mention: true) notifiable_user2 = create(:user, email_me_on_mention: true) unnotifiable_user = create(:user, email_me_on_mention: false) ! MessageMailer.stub(:deliver_message) ! Notifier.notify(message) ! expected(MessageMailer).to have_received(:deliver_message).with(message, [notifiable_user1, notifiable_user2]) end ! it "SMS's the message's mentioned users who prefer to be SMS'd" do notifiable_user1 = create(:sms_user, sms_me_on_mention: true) notifiable_user2 = create(:sms_user, sms_me_on_mention: true) unnotifiable_user = create(:sms_user, sms_me_on_mention: false) ! SMSGateway.stub(:deliver) ! Notifier.notify(message) ! expected_message = "#{message.author.name} said #{message_body}" ! expect(SMSGateway).to have_received(:deliver).with(expected_message, notifiable_user1.sms_number) expect(SMSGateway).to have_received(:deliver).with(expected_message, notifiable_user2.sms_number) end end

class Notifier def self.notify(message) message.mentioned_users. select(&:fb_me_on_mention?). select(&:facebook_connection). each do |user| user.facebook_connection.put_connections( "me", "feed", message: "#{message.author.name} said: #{message.body}" ) end ! email_users = message.mentioned_users. select(&:email_me_on_mention?). select{|u| u.email.present? } MessageMailer.deliver_message(message, email_users) ! message.mentioned_users. select(&:sms_me_on_mention?). select{|u| u.sms_number.present? }. each { |user| SMSGateway.deliver(message, user.sms_number) } end end

Guidelines for Pain-Free Testing ! • defer responsibilities to other classes • assume good abstractions

it "emails the message's mentioned users who prefer to be emailed" it "SMS's the message's mentioned users who prefer to be SMS'd" it "FB's the message's mentioned users who prefer to be FB'd"

it "______ the message's mentioned users who prefer to be ______" it "______ the message's mentioned users who prefer to be ______" it "______ the message's mentioned users who prefer to be ______"

it "______ the message's mentioned users who prefer to be ______"

it "notifies via SMS/FB/Email the message's mentioned users who prefer to be notified via SMS/FB/Email, respectively"

it "notifies the message's mentioned users via their preferred notification channels"

it "notifies the message's mentioned users via notification channels"

it "notifies mentioned users via notification channels"

it "notifies mentioned users via notification channels" do ! message = double('message') channels = [ double(notify_about_message: nil), double(notify_about_message: nil) ] notifier = Notifier.new(channels) ! notifier.notify(message) ! channel[0].should have_received(:notify_about_message).with message channel[1].should have_received(:notify_about_message).with message ! end

class Notifier ! def initialize(channels) @channels = channels end ! def notify(message) @channels.each do |channel| channel.notify_about_message(message) end end ! end ! notifier = Notifier.new(channels) notifier.notify(message)

channels = case Rails.env when 'production' [ EmailChannel.new, SMSChannel.new, NSAChannel.new ] when 'staging' [ TestEmailChannel.new, TestSMSChannel.new ] else [ LoggingChannel.new ] end ! config.notifier = Notifier.new( channels )

it "emails the message's mentioned users who prefer email" do ! message = build(:message, mentioned_users: [ user_who_likes_email1 = build(:user, email_on_mention: true), user_who_likes_email2 = build(:user, email_on_mention: true), user_who_dislikes_email = build(:user, email_on_mention: false) ]) MessageMailer.stub(:deliver_message) ! EmailChannel.new.notify(message) ! MessageMailer.should have_received(:deliver_message) .with(message, [user_who_likes_email1, user_who_likes_email2]) ! end

- notify via channels Notifier - how to notify by email - who prefers to be emailed Email Channel - how to notify by SMS - who prefers to be SMS'd SMS Channel - who prefers to be Facebooked - how to notify by Facebook Facebook Channel - which channels < Configuration > - which users are mentioned Message - email address - Facebook Credentials - SMS number User - notify by email - notify by SMS - notify by Facebook - how to notify by email - who prefers to be emailed - how to notify by SMS - who prefers to be SMS'd - who prefers to be Facebooked - how to notify by Facebook Notifier - which users are mentioned Message - email address - Facebook Credentials - SMS number User

@nicholaides mike@promptworks.com