instance method capture

# File railties/lib/rails/generators/testing/behaviour.rb, line 104
          def capture(stream)
            stream = stream.to_s
            captured_stream = Tempfile.new(stream)
            stream_io = eval("$#{stream}")
            origin_stream = stream_io.dup
            stream_io.reopen(captured_stream)

            yield

            stream_io.rewind
            return captured_stream.read
          ensure
            captured_stream.close
            captured_stream.unlink
            stream_io.reopen(origin_stream)
          end