How can i have rspec test for my default scope

问题:

my model has default_scope(:order => 'created_at' ) my tests (rspec, factory girl, shoulda, etc.) are:

require 'spec/spec_helper.rb'

describe CatMembership do
  context "is valid" do
    subject { Factory.build(:cat_membership) }
    it { should be_valid }
    it { should belong_to :cat}
    it { should belong_to :cat_group}
    it { should have_db_column(:start_date)}
    it { should have_db_column(:end_date)}
  end
end

回答1:

I would rather have this tested using a query and checking the results, but if you really must do it, one possible solution would be something like this for Rails 3:

CatMembership.scoped.to_sql.should == CatMembership.order(:created_at).to_sql

And on Rails 2:

CatMembership.default_scoping.should == [{:create=>{}, :find=>{:order=>"created_at"}}]

But I would not say these solutions are ideal since they show a lot of knowledge of the implementation (and you can see the implementation varies with different Rails versions).

Creating sample data, running an usual all query and checking the result is correctly ordered might have been simpler, would be closer to real unit testing and would work even as you upgrade your rails version.

In this case it would possibly be:

before do
  @memberships = []

  @memberships << CatMembership.create!
  @memberships << CatMembership.create!
  @memberships << CatMembership.create!

  [ 1.hour.ago, 5.minutes.ago, 1.minute.ago ].each_with_index do |time, index|
    membership = @memberships[index]
    membership.created_at = time
    membership.save
  end

end

it 'should be correctly ordered' do
  @sorted_memberships = CatMembership.all
  @memberships.first.should == @sorted_memberships.last
  @memberships.second.should == @sorted_memberships.second
  @memberships.third.should == @sorted_memberships.first
end

It's much more verbose, but it's going to work even as you move forward on rails.

And now I have just noticed who asked the question :D

回答2:

DRY It Up, Use Shared Examples

Most likely, you'll have more than one model with a similar default scope (if not, mostly ignore this method) so you can put this Rspec example into a shared_example where you can call it from a variety of model specs.

My preferred method of checking a default scope is to make sure the default ActiveRecord::Relation has the expected clause (order or where or whatever the case may be), like so:

spec/support/shared_examples/default_scope_examples.rb

shared_examples_for 'a default scope ordered by created_at' do

  it 'adds a clause to order by created_at' do
    described_class.scoped.order_clauses.should include("created_at")
  end

end

And then in your CatMembership spec (and any other spec that has the same default scope), all you need to is:

spec/models/cat_membership_spec.rb

describe CatMembership

  it_behaves_like 'a default scope ordered by created_at'

  # other spec examples #

end

Finally, you can see how this pattern can be extended to all sorts of default scopes and keeps things clean, organized and, best of all, DRY.

回答3:

According to latest conventions of RSpec expect is recommended instead of should so, better answer would be

expect(CatMembership.scoped.to_sql).to eq(CatMembership.order(:created_at).to_sql)

However, lately Model.scoped is deprecated so it is recommended to use Model.all instead

expect(CatMembership.all.to_sql).to eq(CatMembership.order(:created_at).to_sql)