```ruby
# -*- coding: utf-8 -*-
# Copyright 2014 TIS Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
FactoryGirl.define do
  factory :operating_system do
    name 'os_name'
  end

  factory :centos, class: OperatingSystem do
    sequence(:name) { |n| "centos_#{n}" }
  end

  factory :ubuntu, class: OperatingSystem do
    sequence(:name) { |n| "ubuntu_#{n}" }
  end
end
```

Add version to factory for OperatingSystem
user
```ruby
# -*- coding: utf-8 -*-
# Copyright 2014 TIS Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
FactoryGirl.define do
  factory :operating_system do
    name 'os_name'
  end

  factory :centos, class: OperatingSystem do
    sequence(:name) { |n| "centos_#{n}" }
    version '6.5'
  end

  factory :ubuntu, class: OperatingSystem do
    sequence(:name) { |n| "ubuntu_#{n}" }
    version '14.04'
  end
end
```
assistant