```ruby
require File.expand_path(File.dirname(__FILE__) + '/spec_helper')

Dir.glob('locales/*.yml').each do |locale_file|
  describe 'a locale file' do
    it_behaves_like 'a valid locale file', locale_file
    it { locale_file.should be_a_subset_of 'locales/en-US.yml' }
  end
end```

Use en as the source locale (instead of en-US)
user
```ruby
require File.expand_path(File.dirname(__FILE__) + '/spec_helper')

Dir.glob('locales/*.yml').each do |locale_file|
  describe 'a locale file' do
    it_behaves_like 'a valid locale file', locale_file
    it { locale_file.should be_a_subset_of 'locales/en.yml' }
  end
end
```
assistant