Create Valid Instances of the Model Using Factory Bot

Although it’s not a test of our model, creating a model should also involve ensuring there is a way for others to create valid and reasonable instances of the model for other tests. Rails provides a test fixture facility.

Factory Bot is a library to create factories. Factories can be used to create instances of objects more expediently than using new. This is because a factory often sets default values for each field. So, if we want a reasonable Widget instance but don’t care about the values for each attribute, the factory will set them for us. This allows code like so:

widget = FactoryBot.create(:widget)

If we need to specify certain values, create acts very much like new or create on an Active Record:

widget = FactoryBot.create(:widget, name: "Stembolt")

A factory can also create any needed associated objects, so the above invocations will create (assuming we’ve written our factories properly) a manufacturer with an address as well as a widget status.

To generate dummy values, we like to use FakerFaker is a library for generating fake data, such as names, addresses, and phone numbers.. Faker can provide random, fake values for fields of various types. For example, to create a realistic email address on a known safe-for-testing domain like example<span>.com, we can write Faker::Internet.safe_email. ...