Test Devise's registration with Rspec and FactoryGirl - ruby-on-rails

Question

Routes
devise_for :users, controllers: { registrations: 'users/registrations' }
Models
class User < ActiveRecord::Base
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
before_create :set_default_role
enum role_types: [:doctor, :patient]
def set_default_role
set_role :patient unless roles.include? User.role_types[:patient]
end
end
class Patient < User
end
class Doctor < User
end
FactoryGirl
require 'faker'
FactoryGirl.define do
factory :user do
sequence(:name) { |n| "full_name_#{n}" }
address 'valid address'
phone '1234567890'
password 'password'
sequence(:email) { |n| "valid_email_#{n}#example.com" }
end
factory :doctor, class: Doctor, parent: :user do
roles [0, 1]
field
end
factory :patient, class: Patient, parent: :user do
roles [1]
end
end
Registration's spec
require 'spec_helper'
describe Users::RegistrationsController, type: :controller do
before do
#request.env['devise.mapping'] = Devise.mappings[:user]
end
context 'register a patient' do
let(:add_patient) { post :create, patient: FactoryGirl.attributes_for(:patient) }
it { expect { add_patient }.to change(Patient, :count).by(1) }
end
context 'register a doctor' do
let(:add_doctor) { post :create, doctor: FactoryGirl.attributes_for(:doctor) }
it { expect { add_doctor }.to change(Doctor, :count).by(1) }
end
end
When I run the spec, I keep getting this failure for both examples
1) Users::RegistrationsController register a patient should change #count by 1
Failure/Error: it { expect { add_patient }.to change(Patient, :count).by(1) }
expected #count to have changed by 1, but was changed by 0
# ./spec/controllers/registrations_controller_spec.rb:19:in `block (3 levels) in <top (required)>'
My questions are, what causes the failure and how do I debug if my post request is successfully create a user? I know I can use capybara, but in this case I want to make sure if I do the post request for registration, it will register a user.