first you need to adjust the configuration for ldap adapter in example/posix.rb and then start irb
$ LDAP_PWD='secret' irb
require 'example/posix.rb'
u = User.create(:login=>'test', :name => "name", :password => "pwd")
User.all
g = Group.create(:name => "test")
Group.all
u.groups << g
u.groups
g.users
u.authenticate("wrong-pwd")
u.authenticate("pwd")