RSpec fails when using custom validator - ruby-on-rails

Question

I am using such kind of validation in my rails 3.1 project.
validates_presence_of :sales_price
validates_presence_of :retail_price
validates_numericality_of :sales_price, :greater_than => 0,
:allow_blank => true
validates_numericality_of :retail_price, :greater_than => 0,
:allow_blank => true
validate :sales_price_less_than_retail
def sales_price_less_than_retail
if sales_price >= retail_price
errors.add(:sales_price, "must be less than retail price.")
end
end
I'm testing models using rspec. Everything was ok when i used only rails standard validation helpers. But when i wrote custom validator(sales_price_less_than_retail) tests started to fail.
Here is the code of the test:
it { should validate_presence_of :sales_price }
it { should validate_presence_of :retail_price }
it { should validate_numericality_of :sales_price }
it { should validate_numericality_of :retail_price }
Here is the factory:
Factory.define :offer_option do |f|
f.sales_price rand(21) + 10 # $10-$30
f.retail_price { |a| a.sales_price * 2 }
end
When i run the test i get such errors:
Failures:
1) OfferOption
Failure/Error: it { should validate_presence_of :sales_price }
NoMethodError:
undefined method `>=' for nil:NilClass
# ./app/models/offer_option.rb:38:in `sales_price_less_than_retail'
# ./spec/models/offer_option_spec.rb:18:in `block (2 levels) in <top (required)>'
2) OfferOption
Failure/Error: it { should validate_presence_of :retail_price }
ArgumentError:
comparison of BigDecimal with nil failed
# ./app/models/offer_option.rb:38:in `>='
# ./app/models/offer_option.rb:38:in `sales_price_less_than_retail'
# ./spec/models/offer_option_spec.rb:19:in `block (2 levels) in <top (required)>'
I guess everything should be ok because rspec should test validators separately, but it seems that it calls custom validator after calling validates_presence_of in my test.
The problem disappears when i remove custom validator.
What am I doing wrong?

Answer 1

I assume that this is because validate_presence_of rspec helper set offer_option.sales_price = nil and then call valid? on offer_option. When calling valid?, it runs all your validations, so your custom validation as well. And then you get this error, cause there is no '>=' method on nil.
if you change sales_price_less_than_retail to:
def sales_price_less_than_retail
return if sales_prices.blank? || retail_price.blank?
if sales_price >= retail_price
errors.add(:sales_price, "must be less than retail price.")
end
end
Then it should works.