```ruby
require 'pathname'
require 'rubygems'

gem 'rspec', '~>1.1.12'
require 'spec'

require Pathname(__FILE__).dirname.expand_path.parent + 'lib/dm-is-tree'

def load_driver(name, default_uri)
  return false if ENV['ADAPTER'] != name.to_s

  begin
    DataMapper.setup(name, ENV["#{name.to_s.upcase}_SPEC_URI"] || default_uri)
    DataMapper::Repository.adapters[:default] =  DataMapper::Repository.adapters[name]
    true
  rescue LoadError => e
    warn "Could not load do_#{name}: #{e}"
    false
  end
end

ENV['ADAPTER'] ||= 'sqlite3'

HAS_SQLITE3  = load_driver(:sqlite3,  'sqlite3::memory:')
HAS_MYSQL    = load_driver(:mysql,    'mysql://localhost/dm_core_test')
HAS_POSTGRES = load_driver(:postgres, 'postgres://postgres@localhost/dm_core_test')
```

Use RSpec >= 1.1.12 so 1.2 can be used as well
user
```ruby
require 'pathname'
require 'rubygems'

gem 'rspec', '>=1.1.12'
require 'spec'

require Pathname(__FILE__).dirname.expand_path.parent + 'lib/dm-is-tree'

def load_driver(name, default_uri)
  return false if ENV['ADAPTER'] != name.to_s

  begin
    DataMapper.setup(name, ENV["#{name.to_s.upcase}_SPEC_URI"] || default_uri)
    DataMapper::Repository.adapters[:default] =  DataMapper::Repository.adapters[name]
    true
  rescue LoadError => e
    warn "Could not load do_#{name}: #{e}"
    false
  end
end

ENV['ADAPTER'] ||= 'sqlite3'

HAS_SQLITE3  = load_driver(:sqlite3,  'sqlite3::memory:')
HAS_MYSQL    = load_driver(:mysql,    'mysql://localhost/dm_core_test')
HAS_POSTGRES = load_driver(:postgres, 'postgres://postgres@localhost/dm_core_test')
```
assistant