Devise password update testing

I'm trying to test my custom Registration Controller inherited from default Devise Registration Controller.

I created a method to allow user to updates their data without providing the current_password and updates the password providing the current password.

My custom controller

class Users::RegistrationsController < Devise::RegistrationsController
  ...

  def update_resource(resource, params)
    if params[:password].blank? && params[:password_confirmation].blank?
      resource.update_without_password(params)
    else
      super
    end
  end

end

My tests

require "rails_helper"

RSpec.describe Users::RegistrationsController, type: :controller do
  before do
    @request.env['devise.mapping'] = Devise.mappings[:user]
  end
  describe "POST new password" do
    let(:user) { FactoryGirl.create(:user, password: 'current_password', password_confirmation: 'current_password') }
    before do
      login_as(user, :scope => :user)
    end

    context "with an invalid password parameter" do
      it "renders :edit-template" do
        put :update, params: { id: user.id , user: { current_password: "current_password", password: "12", password_confirmation: "12" } }

        expect(response).to render_template(:edit)
      end
    end

    context "with a valid password parameter" do
      it "update user password in database" do
        put :update,  params: { id: user.id, user: { current_password: "current_password", password: "newpassword", password_confirmation: "newpassword" } }
        user.reload

        expect(user.password).to eq("newpassword")
      end
    end
  end
end

I received the follow errors

  1) Users::RegistrationsController POST new password with an invalid password parameter renders :edit-template
 Failure/Error: expect(response).to render_template(:edit)
   expecting <"edit"> but rendering with <[]>
 # ./spec/controller/users/registrations_controller_spec.rb:59:in `block (4 levels) in <top (required)>'

  2) Users::RegistrationsController POST new password with a valid password parameter update user password in database
 Failure/Error: expect(user.password).to eq("newpassword")

   expected: "newpassword"
        got: "current_password"

   (compared using ==)
 # ./spec/controller/users/registrations_controller_spec.rb:68:in `block (4 levels) in <top (required)>'

Any idea what am I doing wrong?