class HelloMessage
  def text
    @text = "Hello World!"
  end
end

class HelloConsole
  def print(text)
    puts text
  end
end

class HelloApp
  def initialize(message, console)
    @message = message
    @console = console
  end

  def printHello
    @console.print(@message.text)
  end
end

message = HelloMessage.new
console = HelloConsole.new
app = HelloApp.new message, console
app.printHello

RSpec.describe HelloMessage do
  it "should return hello world" do
    message = HelloMessage.new
    expect(message.text).to eq("Hello World!")
  end
end

RSpec.describe HelloApp do
  it "should print hello message" do
    messageText = "Hello Test!"

    # 2.1 Create a mock of HelloMessage
    # that will return "Hello Test!" whenever text is called
    message = instance_double("HelloMessage", :text => messageText)

    # 2.2 Create a mock of HelloConsole
    console = instance_double("HelloConsole")
    # 2.3 Expect print to be called once with "Hello Test!"
    expect(console).to receive(:print).once.with(messageText)

    # 2.4 Create a HelloApp, the one we want to test, passing the mocks
    app = HelloApp.new message, console
    # 2.5 Execute the method we want to test
    app.printHello

    # Expectation 2.3 will be checked once test ends
  end
end

HelloApp
  should print hello message

HelloMessage
  should return hello world

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2 examples, 0 failures