require 'test/unit' class TestRedefinition < Test::Unit::TestCase def test_redefinition assert_match /^test\/unit warning: method TestForTestRedefinition#test_redefinition is redefined$/, redefinition end def redefinition(*args) IO.popen([*@options[:ruby], "#{File.dirname(__FILE__)}/test4test_redefinition.rb", *args], err: [:child, :out]) {|f| f.read } end end