Rspec: how to test Service Object method "call" which is called in Controller action create?

Question

Can somebody help me with rspec testing method call in Service Object?

 class UserEntitiesController < ApplicationController
    
      def create
    
        @result = UserEntities::Create.new(params).call
        return render '/422.json.jbuilder', status: :unprocessable_entity unless @result
      end

here is the service objects:

 module UserEntities
  class Create
    attr_accessor :params
    def initialize(params)
      @params = params
    end

    def call
      @user_entity = UserEntity.new(user_entity_params)
      set_time

      if @user_entity.save
        @user_entity
      else
        error_result
      end
    end

    private

    def error_result
      false
    end

    def user_entity_params
      @params.require(:user_entity).permit(:information,
                                           :destroy_option,
                                           :reviews)
    end

    def set_time
      if @params[:available_days].present?
        @user_entity.termination = Time.now + @params[:available_days].days
      end
    end
  end
end

I tried to find information how to do this, but there are not so many. Also i read some

Answer 1

You can certainly write a unit test to test the Service Object standalone

In this case, create a file spec/services/user_entities/create_spec.rb

describe UserEntities::Create do
  let(:params) { #values go here } 

  context ".call" do
    it "create users" do
      UserEntities::Create.new(params).call
      # more test code
    end

    # more tests
  end
end

Later in the controller tests, if you are planning to write such, you do not need to test UserEntities::Create instead you can just mock the service object to return the desired result

describe UserEntitiesController do
  before do
    # to mock service object in controller test
    allow(UserEntities::Create).to receive(:new)
     .and_return(double(:UserEntities, call: "Some Value"))
  end

  # controller tests go here
end