module Minitest::Assertions

def capture_io
  _synchronize do
    begin
      captured_stdout, captured_stderr = StringIO.new, StringIO.new
      orig_stdout, orig_stderr = $stdout, $stderr
      $stdout, $stderr         = captured_stdout, captured_stderr
      yield
      return captured_stdout.string, captured_stderr.string
    ensure
      $stdout = orig_stdout
      $stderr = orig_stderr
    end
  end
end