try this:
require 'spec_helper'
describe PostsController do
describe 'POST #create' do
let(:service_object) { double(:service_object) }
before do
ServiceObject.stub(:new).and_return(service_object)
service_object.stub(:call)
end
it 'calls the service object' do
post :create, post: Fabricate.attributes_for(:post)
expect(service_object).to have_received(:call)
end
end
end