fixed_stdout_spec.rb

# -*- coding: utf-8 -*-
require 'rspec'

describe "stdout" do
  def substitute_stdout
    mock = double('stdout')
    yield mock
    $stdout = mock
  end

  after do
    $stdout = STDOUT            # すり替えた$stdoutを元に戻す
  end

  it "print 'hoge'" do
    substitute_stdout { |stdout|
      stdout.should_receive(:write).with("hoge")
    }
    print "hoge"
  end

  it "puts 'foo' and 'bar'" do
    substitute_stdout { |stdout|
      stdout.should_receive(:write).with("foo").ordered
      stdout.should_receive(:write).with("\n").ordered
      stdout.should_receive(:write).with("bar").ordered
      stdout.should_receive(:write).with("\n").ordered
    }
    puts "foo"
    puts "bar"
  end
end

stdout_spec.rb

# -*- coding: utf-8 -*-
require 'rspec'

describe "stdout" do
  it "print 'hoge'" do
    mock = double("stdout")
    mock.should_receive(:write).with("hoge")
    $stdout = mock

    print "hoge"
  end

  it "puts 'foo' and 'bar'" do
    mock = double("stdout")
    mock.should_receive(:write).with("\n")
    mock.should_receive(:write).with("\n")
    mock.should_receive(:write).with("foo")
    mock.should_receive(:write).with("bar")
    $stdout = mock
    # test passed...
    # how do I check order "foo", "\n", "bar", "\n" ?
    
    puts "foo"
    puts "bar"
  end
end