How to simply stub objects

[ryancheung]

Every time i want to stub an object. I have to do like this:

order =  Object.new
stub(order).item_total { 200 }

Is there any simple way stub a object like what rspec mock does:

  let(:order) { mock('order', item_total: 200) }

[mcmire]

Yes, #stub! will do what you want. So you can say

stub!.item_total { 200 }

Note that you are not able to access the stubbed object in this case, but
if you want that then either say

order = stub! do
  item_total { 200 }
end

or if you expect to only ever have one method you are stubbing then you can
use #subject to get at the object:

order = stub!.item_total { 200 }.subject

HTH.

[ryancheung]

Thank you very much! And I suggest that this usage should be put into the README.

[mcmire]

Yeah it's actually in the API overview: https://github.com/rr/rr/blob/master/doc/03_api_overview.md#double-graphs. I need to clean this section up, though.

[ryancheung]

@mcmire I still have problems here. stub! do item_total { 200 } end would return a instance of RR::DoubleDefinitions::DoubleDefinition, but it should return a instance of Object. While stub!.item_total { 200 }.subject works. It returns a Object with its item_total method stubbed.

[mcmire]

Ah. Actually that makes sense now. You're right, #stub! does return a DoubleDefinition regardless of whether or not you give it a block. So, you want this instead:

order = stub! do
  item_total { 200 }
end.subject

...Only, this doesn't actually work, because I think there's a bug in RR that double-wraps a DoubleDefinition when using the block form. You have to say this instead:

order = stub! do
  item_total { 200 }
end.subject.subject

For this reason I would recommend sticking with the inline form:

order = stub!.item_total { 200 }.subject

If you need to add more methods you can do that easily:

order = stub!.
  item_total { 200 }.
  another_method { :whatever }.
  subject

[ryancheung]

It's not perfect enough, but it works. Thanks for the help!

[mcmire]

Cool glad I could help. I might consider another way to make this more elegant in the future, Mocha and rspec-mocks definitely have RR beat here.

[ryancheung]

@mcmire Yep, they do. But unfortunately, the inline form you recommended not work again now. I got these:

  1) OrderCouponValidator#validate with order that has a coupon_code and the coupon code exists add errors to order if the coupon code 
is not usable
     Failure/Error: changes { {} }.
     NoMethodError:
       undefined method `changes' for #<RR::DoubleDefinitions::DoubleDefinition:0x007f9b0f28bb38>
     # ./spec/models/order_coupon_validator_spec.rb:8:in `block (3 levels) in <top (required)>'
     # ./spec/models/order_coupon_validator_spec.rb:20:in `block (4 levels) in <top (required)>'

The mocking code is:

    let(:order) do
      stub!.
        errors { ActiveModel::Errors.new(Object.new) }.
        changes { {} }.
        subject
    end

I'm using Rails 3.2.13 btw.

Just point out that problem.

[mcmire]

OMG I am so dumb. Of course that doesn't work.

Okay let's try this again:

let(:order) do
  Object.new.tap do |obj|
    stub(obj).item_total { 200 }
    stub(obj).another_method { :whatever }
  end
end

It isn't the most elegant thing in the world but I think that should actually work.

[contentfree]

Commenting on an old, old closed issue, but…

So is the documentation wrong? When I try to use RR as suggested in the docs, eg. mock!.my_method { "something" } I, too, get the undefined method error that @ryancheung got. Can the docs be updated (I know I know, PRs welcome… but what's the "right" way?)

[kou]

First, can you open a new issue with a script that shows the problem and is runnable?