require 'stringio'

def capture_stdout(&blk)
  old = $stdout
  $stdout = fake = StringIO.new
  blk.call
  fake.string
ensure
  $stdout = old
end

def capture_stderr(&blk)
  old = $stderr
  $stderr = fake = StringIO.new
  blk.call
  fake.string
ensure
  $stderr = old
end