> This leads to a loss of a valuable chance of test. =A0It is good for
> test/unit to detect and warn such a redefinition.

I think you can already see them with warning enabled:
(in Ruby 1.9.2)
test.rb:163: warning: method redefined; discarding old test_one
test.rb:160: warning: previous definition of test_one was here
(in 1.8.7)
test.rb:163: warning: method redefined; discarding old test_one

B.D.