Why do I get "undefined method 'has_password?' for nil:NilClass" when I run my test?

railsTutorial-user.rb

require 'digest'
class User < ActiveRecord::Base
  
  attr_accessor   :password
  attr_accessible :name, :email, :password, :password_confirmation
  
  email_regex = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i 
  
  validates :name, :presence => true,
                   :length   => { :maximum => 50 }
  
  validates :email, :presence   => true,
                    :format     => { :with => email_regex },
                    :uniqueness => { :case_sensitive => false }
  
  validates :password, :presence     => true,
                       :confirmation => true,
                       :length       => { :within => 6..40 }

   before_save :encrypt_password 
   
   def has_password?(submitted_password) 
     encrypted_password == encrypt(submitted_password) 
   end 
   
   private 
    
     def encrypt_password 
       self.salt = make_salt if new_record? 
       self.encrypted_password = encrypt(password) 
     end 
    
     def encrypt(string) 
       secure_hash("#{salt}--#{string}") 
     end 
    
     def make_salt 
       secure_hash("#{Time.now.utc}--#{password}") 
     end 
    
     def secure_hash(string) 
       Digest::SHA2.hexdigest(string) 
     end                   
    
end

user_spec.rb

describe "has_password? method" do
    
    it "should be true if the passwords match" do
      @user.has_password?(@attr[:password]).should be_true
    end
    
    it "should be false if the passwords don't match" do
      @user.has_password?("invalid").should be_false
    end
    
  end

If you are following the Tutorial book (I think so),
it works if the test is within the following:

describe "password encryption" do
before(:each) do
@user = User.create!(@attr)
end
...
end