class Test::Unit::Assertions::AssertionMessage::MaybeContainer

def inspect
  if @value.is_a?(Array)
    values = @value.collect do |value|
      @formatter.call(AssertionMessage.convert(value))
    end
    "[#{values.join(', ')}]"
  else
    @formatter.call(AssertionMessage.convert(@value))
  end
end