Meetups in Space - Rails edition

Clinics:

• Mon. 12/15 - Add a meetup branch.
  • Use acceptance testing to test-drive the "add a meetup feature"
• Tues. 12/16 - factory-girl branch.
  • Incorporate the factory_girl_rails gem to clean up our tests.
  • Complete other tests.

Using FactoryGirl

Step 1. Adding FactoryGirl

• Add to Gemfile and bundle

group :development, :test do
  # ...
  gem 'factory_girl_rails'
end

Step 2. Create a factory for your model

You can manually create a factory for your model, or it will be created for you if you run rails generate model <MODELNAME>:

$ rails g model user

invoke  active_record
create    db/migrate/20141216151223_create_users.rb
create    app/models/user.rb
invoke    rspec
create      spec/models/user_spec.rb
invoke      factory_girl
create        spec/factories/users.rb

The Factory will look something like this to start:

# spec/factories/users.rb
FactoryGirl.define do
  factory :user do
    # we need to add attributes here
  end
end

We need to add our attributes to our user factory (as well as our migration for creating the users table):

# spec/factories/users.rb
FactoryGirl.define do
  factory :user do
    first_name "Gene"
    last_name "Parmesan"
    sequence(:email) { |n| "#{n}[email protected]"}
    password "superspy"
  end
end

Unique fields

For unique fields, you need to use a sequence. All of our FactoryGirl-created objects can have the same name, but they can't have the same email. A sequence allows you to insert a number into your email attribute (in this example) to make it unique.

FactoryGirl.define do
  factory :user do
    # ...
    sequence(:email) { |n| "#{n}[email protected]"}
    # ...
  end
end

Associated objects

OK, we've got a factory for User. Now let's make one for Meetup, and let's assume for the purposes of this example that a Meetup must belong_to :user.

Whenever we create a Meetup object, we'll want to make sure to also create an associated user object.

FactoryGirl makes this super simple:

# spec/factories/meetups.rb
FactoryGirl.define do
  factory :meetup do
    name "Ice Skating"
    location "Space Frog Pond."
    description "Magnetic ice skating rink simulates gravity."

    association :user
  end
end

Now if I call FactoryGirl.create(:meetup), it'll create two objects: a Meetup object and a User object.

meetup = FactoryGirl.create(:meetup) # creates a meetup and a user
user = meetup.creator # returns the user object that FG created

Actually, FG makes this even simpler and we can just do this:

# spec/factories/meetups.rb
FactoryGirl.define do
  factory :meetup do
    # ...

    user # omg this is also an association whattttt
  end
end

You can also alias factories to give them different names. So if we wanted a meetup to belong_to :creator, class_name: "User", we could do this:

# spec/factories/meetups.rb
FactoryGirl.define do
  factory :meetup do
    # ...

    association :creator, factory: :user
  end
end

Step 3. Use your factories to build objects in your tests.

Strategies

FactoryGirl gives you a few methods to build objects using your factories. Here are the main ones:

• CREATE. Create a persisted User object (like User.create)

  user = FactoryGirl.create(:user)

• BUILD. Create a User object that hasn't yet been persisted to the DB - similar to calling User.new:

  user = FactoryGirl.build(:user)

• BUILD_STUBBED. Sort of pretend to persist an object but don't really. Useful for speeding up your tests if you find you're creating tons of objects in your tests. However, for some things you really do need to persist objects to the DB so you'll need .create instead. (Check out this blog post.)

  user = FactoryGirl.build_stubbed(:user)

• CREATE_LIST. Create a list of objects. Great for testing index pages, for example. (There's also a build_list method.)

  meetups = FactoryGirl.create_list(:meetup, 3)

• ATTRIBUTES_FOR. Doesn't actually create an object, but returns a hash of attributes that we can use for other things. We might use this to test a "user sign up" feature, for example.

  user = FactoryGirl.attributes_for(:users)

Overriding the default attributes

You can override FactoryGirl's default attributes like so:

user = FactoryGirl.create(:user, first_name: "Barry", last_name: "Zuckercorn")

You can manually associate objects in the same way. Say you want to create a user, and then 3 meetups that they created:

my_user = FactoryGirl.create(:user)
meetups = FactoryGirl.create_list(:meetup, 3, user: my_user)

Notes

There's a whole bunch of crazy stuff you can do with FactoryGirl. Read the docs to learn more:

• Getting Started with FactoryGirl
• factory_girl_rails

I'd recommend sticking with these basics, though, rather than going nuts with things like traits, etc.

Protip: Put your factories in a single spec/support/factories.rb file. Or not.

You can stick with the default location for factories (spec/factories/<MODELNAME_PLURAL>.rb) if you want. I prefer to put my factories in a single file in the spec/support directory (which you may need to create manually). I think it's a pain to have to look at a whole bunch of files to see my factories.

# spec/support/factories.rb
FactoryGirl.define do
  factory :user do
    # ...
  end

  factory :meetup do
    # ...
  end

  factory :rsvp do
    # ...
  end

  # etc.
end

If you do that, though, you need to tell RSpec to load your factories by uncommenting the following line in your rails_helper.rb file:

Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }

[Aside: Now you can put whatever helpers you want in the spec/support directory, in addition to factories.]