NO excessive database interaction

Persisting to the database takes far longer than initializing objects in memory, and 
while we’re talking fractions of a second, each of these round trips to the database 
adds up when running your entire suite.

When you initialize new objects, try to do so with the least overhead. Depending
on what you need, you should choose your initialization method in this order:

Object.new - initializes the object without FactoryGirl. Use this when you
  don’t care about any validations or default values.
FactoryGirl.build_stubbed(:object)-initializestheobjectwithFactoryGirl,
  setting up default values and associates records using the build_stubbed
  method. Nothing is persisted to the database.
FactoryGirl.build(:object) - initializes the object with FactoryGirl, setting
  up default values and persisting associated records with create.
FactoryGirl.create(:object) - initializes and persists the object with Fac-
  toryGirl, setting up default values and persisting associated records with
  create.