def array_diff(array1, array2, format = :text)
    string1 = array1.join("\n") + "\n"
    string2 = array2.join("\n") + "\n"
    Diffy::Diff.new(string1, string2).to_s(format)
  end
def array_diff(array1, array2, format = :text)
    string1 = array1.join("\n") + "\n"
    string2 = array2.join("\n") + "\n"
    Diffy::Diff.new(string1, string2).to_s(format)
  end
Shows a visual diff of 2 arrays by comparing the string representations
 of the arrays with one element per line.
 @param format can be any valid Diffy option, e.g. :color
     see https://github.com/samg/diffy/blob/master/lib/diffy/format.rb