How would you rewrite this test for instantiating a new class?

Testing
1

I have an existing method for a Post model that looks like this:

def send_update_email
  PostEmail.deliver(self)
end

with the corresponding, passing rspec test:

context 'send_update_email' do
  it 'delegates to PostEmail' do
    post = create_post #separate method that uses factory girl
    expect(PostEmail).to receive(:deliver).with(post)
    post.send_update_email
  end
end

The PostEmail class has this class method:

def self.deliver(post)
  new(post).deliver
end

This looks to me like it’s just initiating the instance and then calling the ‘deliver’ instance method.

I would like to remove that class method in PostEmail so I can rewrite the original method like this:

def send_update_email
  PostEmail.new(self).deliver
end

but I can’t figure out how to rewrite the test to get it to pass.

I don’t really understand how the existing test is working since wouldn’t you usually would use the ‘receive’ method on a mock? In this case it’s just using it on PostEmail.
Any ideas on what I should do here to get this refactoring to work?

2

You can build a double that stands in for the PostEmail instance, and then stub PostEmail so that .new returns the double rather than a PostEmail:

it 'delivers an email with the post' do
  post_email_double = double('post email double', deliver: true)
  allow(PostEmail).to receive(:new) { post_email_double }
  post = create_post

  post.send_update_email

  expect(PostEmail).to have_received(:new).with(post) # want to verify the post was used
  expect(post_email_double).to have_received(:deliver) # want to verify that deliver was called
end

I like putting the expectations at the end rather than before the test so that I can keep the test flow in setup, exercise, then verification in that order.

Hope this helps.

3

Excellent, thank you Geoff!
So putting the expectations at the end is why you would use ‘have_received’ instead of ‘receive’, is that right?

4

That’s correct. In order to do this in RSpec you used to have to use a gem like Bourne, but the functionality was merged into RSpec 2 at some point last year. I think having the expectations always fall at the end makes reading tests easier, as you never have to check back for expectations earlier than the test exercise.

5

Yes, that makes sense. Thanks!