Checking The WHERE CLAUSE clause in rspec testing - ruby-on-rails

Question

I have a named scope in rails and i have model by name Product
class Product < ApplicationRecord
scope :old_products, -> { where("tagged_with = ?","old") }
end
Have any body encountered the process of checking the subject which is using where in the active record and that can check the what where clause does the named scope actually holds
In rspec spec/models/product_spec.rb
describe Product do
describe "checking scope clauses" do
subject { Product.old_products }
its(:where_clauses) { should eq([
"tagged_with = 'old'"
]) }
end
end
end
By the way i use rspec-2.89 version with the rails-5 version so any chances that we can check and verify the where clauses

Answer 1

I personally don't think checking returned SQL of a scope is sufficient. The way I would test old_products is:
describe Product do
describe "scopes" do
describe "old_products" do
let!(:old_product) {Product.create(tagged_with: 'old')}
let!(:not_old_product) {Product.create(tagged_with: 'sth_else')}
subject { Product.old_products }
it "returns the product(s) with tagged_with = old" do
expect(subject).to eq([old_product])
end
end
end
end
If you still want to check the return query, may want to try:
it "..." do
expect(subject.to_sql).to eq("SELECT \"products\".* FROM \"products\" WHERE \"products\".\"tagged_with\" = 'old'")
end

Answer 2

# This is better, more readable syntax for scope declaration
class Product < ApplicationRecord
scope :old_products, -> { where(tagged_with: 'old') }
end
# Something like this would work
describe Product do
context 'scopes' do
# Set up something that will always be excluded from the scopes
let!(:product) { create :product }
let!(:scoped_list) { create :product, 3, tagged_with: tag }
shared_examples_for 'returns scoped records' do
# This should work with shoulda-matchers
# (https://github.com/thoughtbot/shoulda-matchers)
# Could also not use subject and do something like:
# expect(
# described_class.send(scope_name.to_sym)
# ).to contain_exactly(scoped_list)
# and declare let(:scope_name) in your describe blocks
it 'returns scoped products' do
should contain_exactly(scoped_list)
end
end
describe '.old_products' do
subject(:old_products) { described_class.old_products }
let(:tag) { 'old' }
it_behaves_like 'returns scoped records'
end
describe '.other_scope' do
subject(:other_scope) { described_class.other_scope }
let(:tag) { 'other_tag' }
it_behaves_like 'returns scoped records'
end
end
end
There is no value in testing the actual SQL -- it's generated by Rails; what you want to test is that your scope is returning the correct objects
I would use context instead of describe when declaring the scopes test block because you're not describing a class or instance method
Use single quotes instead of double quotes unless you are doing string interpolation -- it's more performant
If you're early in the project and each Product only has a single tag, I would also rename the tagged_with column to be tag

Answer 3

describe Product do
describe "checking scope clauses" do
subject { Product.old_products }
expect(subject.values[:where].instance_values['predicates'].to eq(["tagged_with = 'old'"])
end
end