Estou recebendo esta mensagem de erro:

ERROR["test_profile_display", UsersProfileTest, 2.569931] test_profile_display#UsersProfileTest (2.57s)
NoMethodError:         NoMethodError: undefined method `posts' for nil:NilClass
        app/controllers/users_controller.rb:14:in `show'
        test/integration/users_profile_test.rb:22:in `block in <class:UsersProfileTest>'
    app/controllers/users_controller.rb:14:in `show'
    test/integration/users_profile_test.rb:22:in `block in <class:UsersProfileTest>'

Parececharacter no UsersController na linha@posts = @user.character.posts.paginate(page: params[:page]) é nulo. Existe uma relação polimórfica entre usuários e personagens. Eu pensei que tinha usado a sintaxe correta nos dispositivos elétricos para dizer aos trilhos que o usuário Bazley tem um dispositivo elétrico: In characters.yml:

character_bazley:
  sociable: bazley (user)

Como convencer os trilhos de que o equipamento do usuário realmente tem um personagem pertencente a ele?

test / integration / users_profile_test.rb:

require 'test_helper'

class UsersProfileTest < ActionDispatch::IntegrationTest
  include ApplicationHelper

  def setup
    @user = users(:bazley)
  end

  test "profile display" do
    log_in_as(@user)
    get user_path(@user)
    assert_template 'users/show'
    assert_select 'title', full_title(@user.name)
    assert_select 'h1', text: @user.name
    assert_select 'h1>img.gravatar'
    assert_match @user.character.posts.count.to_s, response.body
    assert_select 'div.pagination'
    @user.character.posts.paginate(page: 1).each do |post|
      assert_match post.content, response.body
    end
  end
end # UsersProfileTest

user.rb:

class User < ActiveRecord::Base

  attr_accessor :remember_token, :activation_token, :reset_token
  has_one  :character, as: :sociable, dependent: :destroy
  .
  .
end

character.rb:

class Character < ActiveRecord::Base

  belongs_to :sociable, polymorphic: true
  has_many   :posts, dependent: :destroy
  validates  :sociable_id, presence: true
end # Character

users.yml:

bazley:
  name: Bazley
  email: [email protected]
  callsign: bazley
  password_digest: <%= User.digest('password') %>
  admin: true
  activated: true
  activated_at: <%= Time.zone.now %>

characters.yml:

character_bazley:
  sociable: bazley (user)

No UsersController:

def show
  @user = User.find_by_callsign(params[:callsign])
  @posts = @user.character.posts.paginate(page: params[:page]) # the line causing the error
  @page_name = "user_page"
  redirect_to root_url and return unless @user.activated
end