New features in RSpec 3

Presented internally at Intercom - https://www.intercom.io

Quick rundown of what has changed in RSpec 3, and some of its interesting new features.

Transcript

1. New features in RSpec 3
2. Announced July 2013
3. Released June 2014
4. Old mock and expectation syntax it "uses the old should-based syntax" do message.stub(:sent_at).and_return(Time.now) message.should_receive(:update_stats).with(:some, :args) message.send_count.should == 10 lambda { message.deliver }.should_not raise_error end
5. New mock and expectation syntax it "uses the new expect and allow based syntax" do allow(message).to receive(:sent_at).and_return(Time.now) expect(message).to receive(:update_stats).with(:some, :args) expect(message.send_count).to eq(10) expect { message.deliver }.to_not raise_error end
6. Old boolean matchers it "had boolean matchers that weren't clear" do # matches the literal value TRUE user.paying_customer?.should be_true # also matches any truthy value user.price_plan.should be_true end
7. New boolean matchers it "clarified how they work by renaming them" do expect(user.paying_customer?).to be_truthy expect(user.price_plan).to be_truthy # only matches literal boolean values expect(user.paying_customer?).to be(true) end
8. Verifying doubles •Only allow you to stub methods that exist •Harder to write tests that pass with broken code
9. class Message def initialize(recipients) @recipients = recipients end def email_addresses @recipients.map(&:email) end end class MessageSender def initialize(message) @message = message end def deliver_message @message.emails.each do |email| deliver_to_email(email) end end def deliver_to_email(email) # snip end end
10. class Message def initialize(recipients) @recipients = recipients end def email_addresses @recipients.map(&:email) end end class MessageSender def initialize(message) @message = message end def deliver_message @message.emails.each do |email| deliver_to_email(email) end end def deliver_to_email(email) # snip end end
11. Using a test double it "sends to each of the recipients" do message = double('Message', :emails => ['one', 'two']) message_sender = MessageSender.new(message) expect(message_sender).to receive(:deliver_to_email).with('one') expect(message_sender).to receive(:deliver_to_email).with('two') message_sender.deliver_message end
12. Using an instance double it "sends to each of the recipients" do message = instance_double('Message', :emails => ['one', 'two']) message_sender = MessageSender.new(message) expect(message_sender).to receive(:deliver_to_email).with('one') expect(message_sender).to receive(:deliver_to_email).with('two') message_sender.deliver_message end
13. Using an instance double 4) MessageSender#deliver_message sends to each of the recipients Failure/Error: message = instance_double('Message', :emails => ['one', 'two']) Message does not implement: emails # ./instance_double_spec.rb:6:in `block (3 levels) in <top (required)>'
14. Using a partial double it "sends to each of the recipients" do message = Message.new([]) expect(message).to receive(:emails).and_return(['one', 'two']) message_sender = MessageSender.new(message) expect(message_sender).to receive(:deliver_to_email).with('one') expect(message_sender).to receive(:deliver_to_email).with('two') message_sender.deliver_message end
15. Verifying partial doubles RSpec.configure do |config| config.mock_with :rspec do |mocks| mocks.verify_partial_doubles = true end end # Or, if you’re in a hurry RSpec::Mocks.configuration.verify_partial_doubles = true
16. Compound expectations •Chain expectations together with `and` / `or` •Reduce duplication, group related expectations •Easy to abuse, but useful in some cases
17. Without compound expectations it "creates a user" do expect { app.create_user_and_message }.to change(User, :count).by(1) end it "creates a message" do expect { app.create_user_and_message }.to change(Message, :count).by(1) end
18. With compound expectations it "creates a user and a message" do expect { app.create_user_and_message }.to change(User, :count).by(1) .and change(Message, :count).by(1) end
19. Composable matchers •Describe nested structures using matchers •Less brittle, less tedious to write expectations
20. Without composable matchers it "returns two auto messages and a manual message" do messages = app.messages expect(messages[0]).to be_an(AutoMessage) expect(messages[1]).to be_an(AutoMessage) expect(messages[2]).to be_a(ManualMessage) end
21. With composable matchers it "returns two auto messages and a manual message" do messages = app.messages expect(messages).to contain_exactly( an_instance_of(AutoMessage), an_instance_of(AutoMessage), an_instance_of(ManualMessage) ) end
22. Are we running it yet? intercom — RSpec 3.1 muster — RSpec 2.99 ami-builder — RSpec 3.0 banjaxed — RSpec 3.1 pulse — RSpec 3.0 engage — RSpec 3.0 intercom-user-service — RSpec 2.99 intercom-messages-service — RSpec 3.1 intersearch — RSpec 3.1 hustle — RSpec 3.0 muster-builder — RSpec 3.0 muster-deployer — RSpec 3.0 [REDACTED] [REDACTED]
23. http://myronmars.to/n/dev-blog Read Myron Marston’s blog
24. https://twitter.com/rspec Follow RSpec on Twitter