Shoulda and before_ callbacks

Question

I have simple model:

class Category < ActiveRecord::Base
  belongs_to :board
  validates :name, presence: true, uniqueness: {scope: :board_id}
  validates :board, presence: true
  validates :display_order, presence: true, uniqueness: {scope: :board_id}

  before_save :set_display_order

  private

  def set_display_order
    last = self.board.categories.order("display_order DESC").last
    self.display_order = last.display_order + 100 if last
  end
end

When I added this before_save callback, these tests start to fail:

  it { should validate_uniqueness_of(:display_order).scoped_to(:board_id) }
  it { should validate_uniqueness_of(:name).scoped_to(:board_id) }

With error (this if for the line in private method last = ...):

 NoMethodError:
   undefined method `categories' for nil:NilClass

Other shoulda tests work fine:

  it { should validate_presence_of(:name) }
  it { should validate_presence_of(:board) }
  it { should belong_to :board }

Any idea what is problem here? I tried to change before_save to before_validation but still the same.

gotva · Answer 1 · 2013-10-16T18:33:30.667

Because shoulda creates record in DB. Gem creates record skipping validations

http://rubydoc.info/github/thoughtbot/shoulda-matchers/master/Shoulda/Matchers/ActiveModel#validate_uniqueness_of-instance_method Ensures that the model is invalid if the given attribute is not unique. It uses the first existing record or creates a new one if no record exists in the database. It simply uses ':validate => false' to get around validations, so it will probably fail if there are 'NOT NULL' constraints. In that case, you must create a record before calling 'validate_uniqueness_of'.

In your case created category is empty it means category.board # => nil and you call method categories from nil.

You should create a record yourself for tests on uniqueness.

score 1 · Answer 2 · edited Mar 29 '16 at 22:25

One way around this limitation of shoulda_matchers and AR callbacks is to redefine the subject of the test which shoulda matchers uses.

example:

# category_spec.rb

# assuming you're using factorygirl and have this setup correctly
let(:board) { FactoryGirl.create(:board, :with_many_categories) }
subject { FactoryGirl.build(:category, board: board) }

# your shoulda matcher validations here

Shoulda and before_ callbacks

2 Answers2