gistfile1.rb

❯ cat asd.rb                                                                                                      rubinius/git/master !
require 'test/unit'

class TestFoo < Test::Unit::TestCase
  def test_foo
    obj1 = Object.new
    obj2 = obj1.dup
    def obj1.to_ary
      raise
    end
    assert_equal([obj2], [obj1].flatten)
  end
end
❯ ruby1.8 -v                                                                                                      rubinius/git/master !
ruby 1.8.7 (2012-02-08 patchlevel 358) [x86_64-linux]
❯ ruby1.8 asd.rb                                                                                                  rubinius/git/master !
Loaded suite asd
Started
E
Finished in 0.000165 seconds.

  1) Error:
test_foo(TestFoo):
RuntimeError: 
    asd.rb:8:in `to_ary'
    asd.rb:10:in `flatten'
    asd.rb:10:in `test_foo'

1 tests, 0 assertions, 0 failures, 1 errors
❯