severity.rb

class Severity
  include Comparable
  attr_reader :value
  ORDER = %i[low medium high]

  def self.[](value)
    new(value)
  end

  def initialize(value)
    @value = value
  end

  def <=>(other)
    ORDER.index(@value) <=> ORDER.index(other.value)
  end

  def inspect
    "Severity[:#{@value}]"
  end
end

pp [Severity[:high], Severity[:low]].sort 

# Output
# [Severity[:low], Severity[:high]]