FactoryGirl traits are a great way to encapsulate a set of properties into convenient and meaningful names. Using traits effectively is a simple way to drastically improve the expressiveness of your specs.

The 2.0 release of the FactoryGirl RSpec gem includes a major change that now treats traits as first class citizens. When you instantiate a FactoryGirl object instance with traits, the FactoryGirl RSpec gem will now automatically name your local variable to include the traits as part of the variable definition.

describe User do
  describe '#some_method' do
    with :user, :without_first_name
    it 'works as expected' do
      # notice the variable name includes the trait!
      user_without_first_name.some_method
    end
  end
end

Keeping your variable names in sync with the declared factory/traits makes your specs much more expressive. This also means it is now possible to write a spec that relies on multiple instances of the same factory, and each instance can have different traits.

describe User do
  describe '#some_method' do
    with :user, :without_first_name
    with :user, :without_last_name
    it 'works as expected' do
      # notice each instance maps to the proper set of traits!
      user_without_first_name.some_method
      user_without_last_name.some_method
    end
  end
end

After using this change, it’s hard to imagine ever going back to a test suite that uses generic variable names for the instantiated factory objects.