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Gotchas with commonly used gems

###Acts-as-taggable-on or Acts-as-follower

####Using Taggables with UUIDs

When using the acts-as-taggable-on gem it will generate migrations for the taggable tables with the command

rake acts_as_taggable_on_engine:install:migrations

If the database is set up using UUIDs as opposed to integer IDs then edit the migration whose title looks like

..._acts_as_taggable_on_migration.acts_as_taggable_on_engine.rb

and change this line

t.references :taggable, polymorphic: true

to

t.references :taggable, polymorphic: true, type: :uuid

Monban

Case-insensitive lookup

We use Monban for email (or username) and password authentication. By default, Monban does not treat email (or username, or other lookup fields) as case-insensitive. Thus, a user with email geneparmesan@example.com will not be able to log in if enters GeneParmesan@example.com. This will not stand. The fix is this:

config/initializers/monban.rb

Monban.configure do |config|
  # sub in email for username or other lookup field as necessary
  config.find_method = ->(params) { Monban.config.user_class.find_by(email: params[:email].downcase) }
end

Note also that your validation for email should be case-insensitive:

validates :email, uniqueness: { case_sensitive: false }

(Benn: note, by changing our configuration this way, we are exposing ourselves to an edge case where some email server might actually use case-sensitive email addresses. Technically, according to RFC 2821, email addresses are supposed to be case sensitive. That said, this is extremely unlikely, as any reasonable email system would block two addresses that differ only by case)

Shoulda

Uniqueness validations

When testing uniqueness validations, if you also have a uniqueness constraint on the database, and not just on the model, you need to create a record before running the test or you'll get an error.

# spec/models/widget_spec.rb

it do
  create(:widget)
  should validate_uniqueness_of(:name)
end

If you omit create(:widget), you'll get an error like the following:

1) Widget validations should require case sensitive unique value for name
     Failure/Error: should validate_uniqueness_of(:name)
     ActiveRecord::StatementInvalid:
       PG::NotNullViolation: ERROR:  null value in column "some_other_required_column" violates not-null constraint
       DETAIL:  Failing row contains (02fe5585-93d6-44fb-a79d-3ea4e1f806bf, 2016-01-12 13:30:23.569997, 2016-01-12 13:30:23.569997, a, null, null).
       : INSERT INTO "widgets" ("name", "created_at", "updated_at") VALUES ($1, $2, $3) RETURNING "id"

UPDATE 2/29/16: As of shoulda-matchers version 3.1, this error no longer occurs. Instead, if you fail to create a record in your test, you'll get an error like the following:

1) Widget validations should require case sensitive unique value for name
   Failure/Error: it { should validate_uniqueness_of(:name) }
   Shoulda::Matchers::ActiveRecord::ValidateUniquenessOfMatcher::ExistingRecordInvalid:
     validate_uniqueness_of works by matching a new record against an
     existing record. If there is no existing record, it will create one
     using the record you provide.

     While doing this, the following error was raised:

       PG::NotNullViolation: ERROR:  null value in column "name" violates not-null constraint
       DETAIL:  Failing row contains (ee2c4076-bf42-4902-b932-116e4843ec58, 2016-02-29 18:13:06.84585, 2016-02-29 18:13:06.84585, null, null).
       : INSERT INTO "widgets" ("created_at", "updated_at") VALUES ($1, $2) RETURNING "id"

     The best way to fix this is to provide the matcher with a record where
     any required attributes are filled in with valid values beforehand.
   # ./spec/models/widget_spec.rb:16:in `block (3 levels) in <top (required)>'

Inclusion validation

If you have an inclusion validation like so:

# spec/models/widget_spec.rb

it { should validate_inclusion_of(:name).in_array(['Widgetron', 'Widgetron Deluxe']) }

be aware that it may fail if: (a) you have a uniqueness constraint on name and (b) have already created a record with that name in your database, for example in a before :each or let block:

let!(:widget) { create(:widget) }

it { should validate_uniqueness_of(:name) }
# will fail with an error suggesting the array in the test does not match the
# array you're using to validate in the model, which is false and misleading.
it { should validate_inclusion_of(:name).in_array(['Widgetron', 'Widgetron Deluxe']) }