Testing a sweeper with RSpec in Rails

Question

I want to make sure my sweeper is being called as appropriate so I tried adding something like this:

it "should clear the cache" do
    @foo = Foo.new(@create_params)
    Foo.should_receive(:new).with(@create_params).and_return(@foo)
    FooSweeper.should_receive(:after_save).with(@foo)
    post :create, @create_params
end

But I just get:

<FooSweeper (class)> expected :after_save with (...) once, but received it 0 times

I've tried turning on caching in the test config but that didn't make any difference.

Answer 1

As you already mentioned caching has to be enabled in the environment for this to work. If it's disabled then my example below will fail. It's probably a good idea to temporarily enable this at runtime for your caching specs.

'after_save' is an instance method. You setup an expectation for a class method, which is why it's failing.

The following is the best way I've found to set this expectation:

it "should clear the cache" do
  @foo = Foo.new(@create_params)
  Foo.should_receive(:new).with(@create_params).and_return(@foo)

  foo_sweeper = mock('FooSweeper')
  foo_sweeper.stub!(:update)
  foo_sweeper.should_receive(:update).with(:after_save, @foo)

  Foo.instance_variable_set(:@observer_peers, [foo_sweeper])      

  post :create, @create_params
end

The problem is that Foo's observers (sweepers are a subclass of observers) are set when Rails boots up, so we have to insert our sweeper mock directly into the model with 'instance_variable_set'.

Answer 2

Sweepers are Singletons and are instantiated at the beginning of the rspec test. As such you can get to it via MySweeperClass.instance(). This worked for me (Rails 3.2):

require 'spec_helper'
describe WidgetSweeper do
  it 'should work on create' do
    user1 = FactoryGirl.create(:user)

    sweeper = WidgetSweeper.instance
    sweeper.should_receive :after_save
    user1.widgets.create thingie: Faker::Lorem.words.join("")
  end
end

Answer 3

Assuming you have:

• a FooSweeper class
• a Foo class with a bar attribute

foo_sweeper_spec.rb:

require 'spec_helper'
describe FooSweeper do
  describe "expiring the foo cache" do
    let(:foo) { FactoryGirl.create(:foo) }
    let(:sweeper) { FooSweeper.instance }
    it "is expired when a foo is updated" do
      sweeper.should_receive(:after_update)
      foo.update_attribute(:bar, "Test")
    end
  end
end