Configuration.rb

class CreateConfigurations < ActiveRecord::Migration
  def self.up
    create_table :configurations do |t|
      t.string :key
      t.text :value
      t.timestamps
    end
    add_index :configurations, :key, :unique => true
  end

  def self.down
    remove_index :configurations, :key, :unique => true
    drop_table :configurations
  end
end


class Configuration < ActiveRecord::Base
  serialize :value
  validates_uniqueness_of :key
  
  class << self
  
    def get(key)
      Rails.cache.fetch("Config.#{key}") {
        find_by_key(key.to_s).try(:value)
      }
    end
  
    def set(key, value)
      c = find_or_initialize_by_key(key.to_s)
      c.update_attribute(:value, value)
      Rails.cache.write("Config.#{key}", value)
    end
    
    alias :defined? :get
    alias :[]= :set
    alias :[] :get

  end
end


require 'test_helper'

class ConfigurationTest < ActiveSupport::TestCase

  test "setting a string configuration" do
    Configuration.set(:a_str, 'This is a string')
    assert Configuration.get(:a_str).is_a?(String)
    assert_equal 'This is a string', Configuration.get(:a_str)
  end
  
  test "setting an integer configuration" do
    Configuration.set(:an_int, 42)
    assert Configuration.get(:an_int).is_a?(Integer)
    assert_equal 42, Configuration.get(:an_int)
  end
  
  test "setting any other marshalable object" do
    Configuration.set(:anything, {:hash => 'works too'})
    assert Configuration.get(:anything).is_a?(Hash)
  end
  
  test "retrieving non-existant key should be nil" do
    assert_nil Configuration.get(:dont_exist)
  end

  test "additional alias for defined?" do
    assert Configuration.respond_to?(:defined?)
  end  
  
  test "caching support" do
    Rails.cache.write('Config.foo', 'blah')
    assert_equal 'blah', Configuration.get('foo')
  end

  test "key based support" do
    Configuration['test'] = 'example'
    assert_equal 'example', Configuration['test']
  end

end