http://collectiveidea.com/blog/archives/2014/08/06/time-to-bring-back-fixtures/
blog-post-time-to-bring-back-fixtures#why-are-factories-problematic "Unfortunately, due to the fact that factories have to create data for every test, and with how easy it is to set up very deep object associations under a single factory invocation, many apps are now in the situation where the tests create so much data that they are unbearably slow. Not only are factories entering rows into the database but they're also allocating Ruby objects, running ActiveRecord callbacks and validations (often across associations), and then garbage collecting all of these objects. For every test. This stack has proven difficult to optimize or improve." blog-post-time-to-bring-back-fixtures#why-are-factories-problematic