snippet

# Find out what storage engines are installed and this supported by datamapper
# This could be especially useful in testing scenarios, where one wants to run
# specs against all adapters that are available on the machine in use.

require "rubygems"
require "dm-core"
require "spec"

module DataMapper

  def self.available_storage_engines
    [ :sqlite3, :mysql, :postgres ].select do |name|
      storage_engine_available?(name)
    end
  end

  def self.storage_engine_available?(name)
    ::DataObjects.const_defined?(Extlib::Inflection.classify(name.to_s))
  end

end

# spec helper
# set it so that it fits your actually installed do_xxx drivers
AVAILABLE_STORAGE_ENGINES = [
  :sqlite3,
  :mysql
  # :postgres
]

describe 'DataMapper storage engine reflection: ' do

  describe 'DataMapper.storage_engine_available?(name)' do
    it 'should return true for adapters known to be installed on this machine' do
      DataMapper.storage_engine_available?(:sqlite3).should  == AVAILABLE_STORAGE_ENGINES.include?(:sqlite3)
      DataMapper.storage_engine_available?(:mysql).should    == AVAILABLE_STORAGE_ENGINES.include?(:mysql)
      DataMapper.storage_engine_available?(:postgres).should == AVAILABLE_STORAGE_ENGINES.include?(:postgres)
    end
  end

  describe 'DataMapper.available_storage_engines' do
    it 'should try all adapters shipped with dm-core and return all adapters known to be installed on this machine' do
      storage_engines = DataMapper.available_storage_engines
      storage_engines.size.should == AVAILABLE_STORAGE_ENGINES.size
      storage_engines.each do |storage_engine|
        AVAILABLE_STORAGE_ENGINES.should include(storage_engine)
      end
    end
  end

end

# mungo:Desktop snusnu$ spec -cfs storage_engine_reflection.rb
#
# DataMapper storage engine reflection:  DataMapper.storage_engine_available?(name)
# - should return true for adapters known to be installed on this machine
#
# DataMapper storage engine reflection:  DataMapper.available_storage_engines
# - should try all adapters shipped with dm-core and return all adapters known to be installed on this machine
#
# Finished in 0.002688 seconds
#
# 2 examples, 0 failures