test_helper.rb

def keep_stdout(&block)
  begin
    orig_stream, $stdout = $stdout, StringIO.new
    block.call($stdout)
  ensure
    s, $stdout = $stdout.string, orig_stream
    s
  end
end

# Used to test exact STDOUT output
def assert_output(expected, &block)
  keep_stdout do |stdout|
    block.call
    if expected.is_a?(Regexp)
      assert_match expected, stdout.string
    else
      assert_equal expected.to_s, stdout.string
    end
  end
end

# Used to test if STDOUT contains a certain substring
def assert_output_include?(expected, &block)
  keep_stdout do |stdout|
    block.call
    assert_equal true, stdout.string.include?(expected.to_s)
  end
end