Rails fixtures vs seeds

Question

I'm learning Ruby on Rails, and I'd like to just make sure I understand the difference between fixtures and seed data.

What I understand is that fixtures are basically test data that you run your testing assertions against, and have no persistence as soon as your tests are done, whereas seeds you put into the database automatically when you do something like rake db:seed.

Why use seeds in this case? Just to avoid having to write out all the myriad testing assertions? For data that you know will need to be in the database when the app is brought into production?

(I guess, static data that would always have been there like the first admin on a message board?)

Answer 1

You got it right. Seed data is to populate the database with prerequisite data needed to allow the app to be usable from the beginning, like to add a default admin account which is required for the app to be managable from the start.

Seed data should not be used for testing purpose, while testing you should always make sure the database is clean so that you know that the only data used by an example is the data populated by the example it self not from any where outside, this allows to avoid confusion.

fixtures is one way of doing this. but a better way is to use factories like factory girl, check this railscast episode for a better explanation.