Cancancan ability debugging fails in rails console and Rspec

I have this in models/ability.rb

class Ability
  include CanCan::Ability

  def initialize(user)
    user ||= User.new   

    if user.role? :registered
      can :read Post
    end

  end

When I do this on rails console

#this returns a user with a role: "registered" attribute   
user = User.first
post = Post.first
ability = Ability.new(user)

### This returns false ###
ability.can?(:read, post)
#=> false

This spec I have written to test the ability also fails while i expect it to pass.

describe User, :type => :model do
  let(:post) {create(:post)}
  describe "abilities" do
    subject(:ability){Ability.new(user)}
    let(:user){nil}

     context "when is a registered user" do

       ## the default value for the role attribute in the user factory is "registered"
       let(:user) {create(:user)}
       it {is_expected.to be_able_to :read, post}
     end
  end
end

I can access and read posts in both /posts and /posts/:id when I am authenticated as a registered user on the browser, I have no idea why it is failing in both rails console and rspec.

Following our discussion, we concluded that the problem is either

1. Rails didn't load the Ability class, or
2. A code somewhere somehow overrides the Ability class.

The workaround-solution is to manually load the Ability file by appending the following at the end of the application.rb

require "#{Rails.root}/app/models/ability.rb"