Testing Associations With RSpec in a Chess Application - ruby-on-rails

Question

I'm currently working with a small team on an open source Rails 4 chess application, and I'm trying to test out various possible piece moves in RSpec (including special cases such as en passant and castling). A senior web developer suggested that I use a separate table to keep track of the moves taken in each game of chess. After taking him up on his suggestion, I'm having trouble testing out valid moves, as shown in the error message below. I suspect that it might be a problem with my associations, but the teammates that I was able to talk to about this were unsure about the cause.
Any help would be greatly appreciated.
Error message:
Failures:
1) PiecesController Action: pieces#update should create a move when a move is valid
Failure/Error: #current_game ||= current_piece.game
NoMethodError:
undefined method `game' for nil:NilClass
# ./app/controllers/pieces_controller.rb:36:in `current_game'
# ./app/controllers/pieces_controller.rb:40:in `require_authorized_for_current_game'
# ./spec/controllers/pieces_controller_spec.rb:12:in `block (3 levels) in <top (required)>'
The test:
RSpec.describe PiecesController, type: :controller do
describe "Action: pieces#update" do
it "should create a move when a move is valid" do
user_sign_in
game = FactoryGirl.create(:game)
# Test a white pawn's movement on its first turn:
piece = FactoryGirl.create(:piece)
move = FactoryGirl.create(:move)
# Why can't I call game.id below?
patch :update, :id => game.id, :pieces => { }
piece_params = { :x_position => piece.x_position, :y_position => piece.y_position, :type => "Pawn" }
if piece.valid_move?(piece_params)
...
end
end
end
private
def user_sign_in
user = FactoryGirl.create(:user)
sign_in user
end
end
Associations:
class Game < ActiveRecord::Base
has_many :pieces
has_many :moves, through: :pieces
belongs_to :white_player, class_name: 'User', foreign_key: :white_player_id
belongs_to :black_player, class_name: 'User', foreign_key: :black_player_id
...
end
class Piece < ActiveRecord::Base
belongs_to :game
has_many :moves
def valid_move?(params)
...
end
...
end
class Move < ActiveRecord::Base
belongs_to :piece
end
Factories:
FactoryGirl.define do
factory :user do
...
end
factory :game do
association :white_player, factory: :user
association :black_player, factory: :user
turn 1
end
factory :piece do
association :game
...
end
# Set up an initially empty move, then adjust the values after checking that a piece can be moved:
factory :move do
association :piece
...
end
end
The controller:
class PiecesController < ApplicationController
before_action :authenticate_user!
before_action :require_authorized_for_current_game, only: [:update]
before_action :require_authorized_for_current_piece, only: [:update]
def update
...
end
...
private
def current_piece
#current_piece ||= Piece.find_by_id(params[:id])
end
...
def piece_params
params.require(:piece).permit(:x_position, :y_position, :type, :captured)
end
def current_game
#current_game ||= current_piece.game
end
def require_authorized_for_current_game
if current_game.white_player != current_user && current_game.black_player != current_user
render text: 'Unauthorized', status: :unauthorized
end
end
end