to_param not working in nested polymorphic associated model - ruby-on-rails

Question

This test is failing at the line get_users_path:
require 'test_helper'
class UsersIndexTest < ActionDispatch::IntegrationTest
def setup
#admin = users(:user_baz)
end
test "index as admin including pagination and delete links" do
log_in_as(#admin)
get users_path
.
.
end
end
Here is the error message:
ActionView::Template::Error: undefined method 'callsign' for nil:NilClass
app/models/user.rb:35:in 'to_param'
app/views/users/_user.html.erb:3:in '_app_views_users__user_html_erb___623096829469928541_2227766840'
app/views/users/index.html.erb:8:in '_app_views_users_index_html_erb__62429272046032246_2224894860'
test/integration/users_index_test.rb:9:in `block in <class:UsersIndexTest>'`
It's referring to the line self.character.callsign in the to_param method in the User model.
User.rb:
class User < ActiveRecord::Base
attr_accessor :remember_token, :activation_token, :reset_token
has_one :character, as: :sociable, dependent: :destroy
accepts_nested_attributes_for :character
has_secure_password
before_validation do
self.create_character unless character
end
before_save do
self.email.downcase!
end
before_create :create_activation_digest
validates :name, presence: true,
length: { maximum: 50 }
VALID_EMAIL_REGEX = /\A[\w+\-.]+#[a-z\d\-]+(?:\.[a-z\d\-]+)*\.[a-z]+\z/i
validates :email, presence: true,
format: { with: VALID_EMAIL_REGEX },
uniqueness: { case_sensitive: false }
validates :password, length: { minimum: 6 }, allow_blank: true
validates :character, presence: true
def to_param
self.character.callsign
end
.
.
end
Character.rb:
class Character < ActiveRecord::Base
belongs_to :sociable, polymorphic: true
before_save do
self.callsign.downcase!
end
VALID_CALLSIGN_REGEX = /\A[a-z\d\-.\_]+\z/i
validates :callsign, presence: true,
length: { maximum: 20 },
format: { with: VALID_CALLSIGN_REGEX },
uniqueness: { case_sensitive: false }
end
app/views/users/index.html.erb:
<% provide(:title, 'All users') %>
<h1>All users</h1>
<%= will_paginate %>
<ul class="users">
<%= render #users %>
</ul>
<%= will_paginate %>
app/views/users/_user.html.erb:
<li>
<%= gravatar_for_user user, size: 52 %>
<%= link_to user.name, user %>
<% if current_user.admin? && !current_user?(user) %>
| <%= link_to "delete", user, method: :delete,
data: { confirm: "You sure?" } %>
<% end %>
</li>
Why is this test failing? Why is self.character.callsign in to_param not working?

Answer 1

It was because I hadn't manually given a character to all the users in test/fixtures. In characters.yml I created a character for every user, and the test passed.