Stdout

require 'stdout'

demo = Stdout::Output.capture { puts "hoge" }

p demo #=> ["hoge\n"]

demo2 = Stdout::Output.capture {
  puts "Hello, "
  puts "World!"
}

p demo2 # => ["Hello, \n", "World!\n"]

require 'stdout'
require 'minitest/autorun'

class YourClass
  def self.some_method
    puts "aaa"
    puts "bbb"
    puts "ccc"
  end
end

class TestYourClass < MiniTest::Unit::TestCase
  def test_some_method
    expected = [
      "aaa\n",
      "bbb\n",
      "ccc\n"
    ]
    result = Stdout::Output.capture{ YourClass.some_method }
    assert_equal(expected, result)
  end
end