rspec stub to allow [hash_key] to be passed - ruby

Question

How do you create a rspec method stub to allow a response from a method that takes in the hash key to return its value?
This is the line I want to test
sub_total = menu.menu_items[item] * quantity
and I'm using this line in rspec as my test stub on a double.
allow(menu).to receive(:menu_items[item]).and_return(2.0)
My env is set up with ruby 2.2.0 and spec 3.1.7
However I keep on getting a
NameError: undefined local variable or method `item'
Ruby code
def place_order(item, quantity, menu)
sub_total = menu.menu_items[item] * quantity
#customer_order << [item, quantity, sub_total]
end
Rspec code
let(:menu) { double :menu }
it "should allow 1 order of beer to placed" do
order = Order.new
allow(menu).to receive(:menu_items[item]).and_return(2.0)
order.place_order(:Beer, 1, 2.0)
expect(order.customer_order).to eq [[:Beer, 1, 2.0]]
end
Failures:
1) Order should allow 1 order of beer to placed
Failure/Error: allow(menu).to receive(:menu_items[item]).and_return(2.0)
NameError:
undefined local variable or method `item' for #<RSpec::ExampleGroups::Order:0x007fbb62917ee8 #__memoized=nil>
# ./spec/order_spec.rb:9:in `block (2 levels) in <top (required)>'
I've tried a number of things but nothing has worked
allow(menu).to receive(:menu_items).and_return(2.0)
allow(menu).to receive(:menu_items).with(item).and_return(2.0)
allow(menu).to receive(:menu_items).with("item").and_return(2.0)
allow(menu).to receive(:menu_items).with([item]).and_return(2.0)
I've run my code in irb and I can see it works but I can't find a way to get my class double to recerive the hash key.

Answer 1

you can do this:
allow(menu.menu_items).to receive(:[]).and_return({Beer: 2.0})
You can also pass an specific item if you need:
allow(menu.menu_items).to receive(:[]).with(1).and_return({Beer: 2.0})

Answer 2

The line menu.menu_items[item] is in reality composed by 3 method calls. [] is a call to the method [] on the Hash returned by menu_items.
I assume menu.menu_items returns a Hash and not an Array, given in the spec item is a Symbol.
That means your stub requires a little bit more work.
allow(menu).to receive(:menu_items).and_return({ Beer: 2.0 })
Also note, the error
undefined local variable or method `item'
is because you were using item in the spec, but item is not defined outside your method.

Answer 3

you're going a little too deep with your stub, think of this instead
allow(menu).to receive(:menu_items).and_return({Beer: 2.0})

Answer 4

Thanks to #SimoneCarletti's answer, I was able to easily stub an instance of PublicActivity. I add this answer only as a more brief (re)statement of the OP's problem and the simplicity of the solution.
Code I want to mimic with a stub:
self.entity = activity.parameters['entity_string']
And the salient parts of the test double:
activity = double('activity') # PublicActivity
allow(activity).to receive(:parameters).and_return({'entity_string' => "some entity name"})
Full code:
class ActivityRenderer
attr_accessor :time
attr_accessor :user
attr_accessor :action
attr_accessor :entity
def initialize(activity)
self.entity = activity.parameters['entity_string']
self.time = activity.updated_at
self.user = User.find(activity.owner_id)
self.action = activity.key
end
end
RSpec.describe ActivityRenderer do
let(:user) { ...factory girl stuff... }
let(:now) { Time.zone.now }
before do
Timecop.freeze
end
it 'provides an activity renderer' do
activity = double('activity') # PublicActivity
allow(activity).to receive(:parameters).and_return({'entity_string' => "some entity name"})
allow(activity).to receive(:updated_at).and_return(now)
allow(activity).to receive(:owner_id).and_return(user._id)
allow(activity).to receive(:key).and_return('some activity?')
ar = ActivityRenderer.new(activity)
expect(ar.user).to eql(user)
expect(ar.time).to eql(now)
expect(ar.action).to eql('some activity?')
expect(ar.entity).to eql("some entity name")
end
end