Test with STDIO

test_sample.rb

require 'minitest/autorun'

class TestMyClass < Minitest::Test

  def setup
    @orig_stdin = $stdin
    @in = StringIO.new
    $stdin = @in
  end

  def teardown
    $stdin = @orig_stdin
  end

  def test_5
    @in << <<'EOS'
5
EOS
    @in.rewind

    out, err = capture_io do
      load("sample.rb")
    end

    assert_equal "5\n", out
  end
end