ruby rspec how to mock a method call with an instance variable

Question

I am trying to write a Rspec test for a ruby function which lives in a new file and references an instance variable inside a controller file. I am having unable to mock anything for the line

flag = @domain.feature?("BrandNewFeature")

When I run the above code I get error on line

flag = @domain.feature?("BrandNewFeature")

saying

#<NoMethodError: undefined method `feature?' for nil:NilClass>

Any help is greatly appreciated

play.rb

Api.controllers :playbooks do
before do
    @domain = account.domain

def get_filter(param)
    f = find_lists(param)

play_help.rb

module ApiHelpers
def find_lists(params)
    flag = @domain.feature?("BrandNewFeature")
    folder = ListQueries.folders(params) if flag
    folder

play_help_spec.rb

require "unit/spec_help"
require_project "api/helpers/play_help.rb"

RSpec.describe ApiHelp do

describe "#find_matching_lists" do
    allow(list_queries).to receive(:folders).and_return(folders)
    binding.pry
    domainDouble = double()
    allow(Domain).to receive(:new).and_return(domainDouble)

    allow(domainDouble).to receive(:feature?).with("BrandNewFeature").and_return(true)

Does this answer your question? How can I mock an instance variable in rspec — Int'l Man Of Coding Mystery
– Int'l Man Of Coding Mystery, Commented Oct 31, 2022 at 18:48
I don't know what account is but it seems like mocking account.domain would be better and easier in this scenario. — engineersmnky
– engineersmnky, Commented Nov 1, 2022 at 17:34

spickermann · Accepted Answer · 2022-11-01 07:27:15Z

0

When you cannot controll the instance that you need to mock then you can use allow_any_instance_of:

RSpec.describe ApiHelp do
  let(:folders) { ... }
  let(:params) { ... }

  before do 
    allow_any_instance_of(Domain)
      .to receive(:feature?).with('BrandNewFeature').and_return(true)
    allow(ListQueries)
      to receive(:folders).with(params).and_return(folders)
  end

  describe '#find_matching_lists' do
    expect(ApiHelp.get_filter).to eq(folders)

    expect_any_instance_of(Domain).to have_received(:feature?).once
    expect(ListQueries).to have_received(folders).once
  end

edited Nov 1, 2022 at 7:27

answered Oct 31, 2022 at 4:54

spickermann

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4 Comments

imba22 Over a year ago

Have you tried this scenario? Is this working for you? I am still getting an error.

spickermann Over a year ago

What error do you get?

imba22 Over a year ago

When I run the test, I see it errors out in play_help.rb. Also in the play_help.rb @domain is coming out Nil (I checked by utting binding.pry) => #<NoMethodError: undefined method `feature?' for nil:NilClass>

spickermann Over a year ago

What is @domain in your helper?

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