title: FactoryBot and Faker - unique is not working
body: <p>I'm using FactoryBot and Faker for my tests, and it looks like that Faker is generating the same name:</p>
  
  <pre><code>class Profile &lt; ApplicationRecord
    belongs_to :user
    validates_presence_of :first_name, :last_name, :nickname
    validates :nickname, uniqueness: { case_sensitive: false }
  end
  
  FactoryBot.define do
    factory :user do
      sequence(:email) { |n| "user#{n}@example.org" }
      password "123456"
      trait :with_profile do
        profile
      end
    end
  end
  
  FactoryBot.define do
    factory :profile do
      first_name Faker::Name.unique.first_name
      last_name Faker::Name.unique.last_name
      nickname { "#{first_name}_#{last_name}".downcase }
      user
    end
  end
  
  RSpec.feature "Friendships", type: :feature do
    scenario "User can accept a pending friendship request" do
      @tom   = create(:user, :with_profile)
      @jerry = create(:user, :with_profile)
      #other stuff
    end
  end
  </code></pre>
  
  <p>Even I'm using the unique method, I'm getting the error </p>
  
  <pre><code>ActiveRecord::RecordInvalid: Validation failed: Nickname has already been taken`.
  </code></pre>
  
  <p>Any clues?</p>