Class methods are not included they are extended, see this gist for further explanation on the major difference between including a module and extending it.

include_vs_extend.rb

module A
  def our_method
    puts "Module A"
  end
end

class Including
  # by including a module we mark its methods as instance methods
  # that can only be used from the object scope
  include A
end

class Extending
  # extending a module marks its methods for being Class-Level methods
  # you can't call them from the object scope
  # only from the class level
  extend A
end

msg = <<EOF
  Hope this illustrated the difference between including
  modules and extending them in ruby, also illustrated
  Ruby's error processing mechanism in details
EOF

[Including, Extending].each do |klass|
  begin
  puts "Working on the #{klass.to_s} class"
  klass.our_method
  rescue NoMethodError => err
    puts err, "We're gonna fix it..."
    klass.new.our_method
  ensure
    puts '-' * 18
  end
end

puts msg