Helper method to format a boolean value. See http://juliankniephoff.wordpress.com/2011/04/09/formatting-boolean-values-in-rails for some documentation.

application_helper.rb

module ApplicationHelper
  def b(value, options = {})
    options = {
      :true => :positive,
      :false => :negative,
      :scope => [:boolean],
      :locale => I18n.locale, # <- It makes easy to avoid conditional run
    }.merge options
    
    # avoid passing nil, or some desctructive value
    # what can be easily happened
    boolean = !!(value || false)
    key = boolean.to_s.to_sym

    t(options[key], :scope => options[:scope], :locale => options[:locale])
  end
end

application_helper_spec.rb

require 'spec_helper'

describe ApplicationHelper do
  context 'method b' do
    it 'translates booleans correclty' do
      I18n.backend.store_translations  :en, :boolean => { :positive => 'yes', :negative => 'no' }
      I18n.locale = :en
      helper.b(true).should eql 'yes'
      helper.b(false).should eql 'no'
    end
  end
end