On
SlimWiki code, one failing test took me a whole day to track down. The worst thing is that the spec passes when the example is run in isolation, but fails when run in a test suite.
rspec spec/features/some_spec.rb:123 # passes
rspec spec/features/some_spec.rb # fails, wtf!
Upon inspection, it turned out that our
factory girl is producing a non-paid account, when asked for a paid account.
pry> FactoryGirl.create(:paid_account).subscription.paid?
=> false
The :paid_account factory declares a :pro_subscription like this:
factory :paid_account, :parent => :account do
association :subscription, :factory => :pro_subscription # ...
end
But that factory works fine:
pry> FactoryGirl.create(:pro_subscription).paid?
=> true
After one day and sprinkling a bit of binding.pry here and there…
factory :paid_account, :parent => :account do
# ...
after(:build) do |account|
binding.pry
end
end
It turned out that after building the :paid_account (but before saving), the subscription is paid, which is correct.
pry> account.subscription.paid?
=> true
After the account is saved, however, it turned into a non-paid account!
pry> account.save!
=> true
pry> account.subscription.paid?
=> false # wtf!!
Something must be changing the global state of the system, but what could it be? One potential cause may be from directly modifying classes to temporarily skip callbacks. So I grepped for skip_callback on our specs, and found this seemingly unrelated factory:
factory :account_without_subscription, :parent => :account do
to_create do |account|
account.class.skip_callback :create, :after, :create_subscription
account.save!
account.class.set_callback :create, :after, :create_subscription
end
end
Sometimes, we want to create an account, but without a subscription. To do that, we temporarily skip the callback before creating the account. After the account has been created, add the callback back to the class again.
Seems legit, right? Now look at our Account.rb:
after_create :create_subscription, :if => 'subscription.blank?'
Notice the :if clause here, and the lack of :if clause in the factory above. This causes the subscription to be unconditionally replaced with a non-paid subscription. Its impact echoes throughout the age of the rspec run, causing any future tests that depend on a paid subscription to fail.
Today, I learned that skipping callbacks — or in general, modifying the behavior of some class at runtime — can be dangerous and error-prone.
An alternative way is to define an accessor:
# Attributes (for tests)
attr_accessor :_skip_creating_subscription
# ...
after_create :create_subscription, :if => 'subscription.blank?',
:unless => :_skip_creating_subscription
The underscore in front of the attribute name means that it’s intended for tests, and not for general use. Our factory became much simpler too:
factory :account_without_subscription, :parent => :account do
_skip_creating_subscription { true }
end
And now we are back to our fabulous run!
