How to test a scope in Rails 3

Question

What\'s the best way to test scopes in Rails 3. In rails 2, I would do something like:

Rspec:

it \'should have a top_level scope\' do
  Category.top         


        

Answer 1

Quickly Check the Clauses of a Scope

I agree with others here that testing the actual results you get back and ensuring they are what you expect is by far the best way to go, but a simple check to ensure that a scope is adding the correct clause can also be useful for faster tests that don't hit the database.

You can use the where_values_hash to test where conditions. Here's an example using Rspec:

it 'should have a top_level scope' do
  Category.top_level.where_values_hash.should eq {"parent_id" => nil}
end

Although the documentation is very slim and sometimes non-existent, there are similar methods for other condition-types, such as:

order_values

Category.order(:id).order_values
# => [:id]

select_values

Category.select(:id).select_values
# => [:id]

group_values

Category.group(:id).group_values
# => [:id]

having_values

Category.having(:id).having_values
# => [:id]

etc.

Default Scope

For default scopes, you have to handle them a little differently. Check this answer out for a better explanation.