gistfile1.rb

Models with their associations

class Reservation < ActiveRecord::Base
  belongs_to :load
  has_one :bid
end

class Load < ActiveRecord::Base
  has_many :bids, :dependent => :delete_all
  has_one :reservation
end

class Bid < ActiveRecord::Base
  belongs_to :load
  belongs_to :reservation
end

The reservation migration only includes the references to the two tables
In my reservations controller I have the following code:

class ReservationsController < ApplicationController
  
  before_filter :find_load
  def new
    @reservation = @load.reservation.build
  end
  
  private
  
  def find_load
    @load = Load.find(params[:load_id])
  end
end

In my config routes file I have the following:
resources :loads do 
    resources :bids
    resources :reservations
  end

When I run my test suite I am getting undefined method build for nil:NilClass, why am I getting this issue?