Validation failed: Reviewer cannot write a review about yourself, Reviewer can't be blank, Reviewee can't be blank

I am writing controller tests for a Rails application where in users can write reviews about others (but not for themselves).

reviews_controller_spec.rb

describe "PATCH update" do
  it "redirects to user_reviews_url" do
    @user = FactoryGirl.create :user
    sign_in @user
    @user1 = FactoryGirl.create :user
    @review = FactoryGirl.attributes_for :review
    post :create, user_id:@user1.id, review:@review
    patch :update, {user_id:@user1.id, id:@review.id}, review: {:description => "john.doeexample1.com"}
    flash[:notice].should_not be_nil
    flash[:notice].should eq("Review was successfully updated.")
    response.should redirect_to(user_path(assigns(:review)))
  end
end

factories.rb

FactoryGirl.define do
  factory :review do
    skill
    stars "4"
    body "limit: 65535"
  end
  factory :skill do
    name "Cooking"
  end
  factory :experience do
    description "abcdfef"
    start_date "1989-11-23"
    level "4"
    skill
  end
  factory :user do |u|
    u.sequence(:first_name) { |n| "Michael#{n}"}
    u.last_name      "Harlt"
    u.sequence(:email) { |n|  "michael#{n}@example.com"}
    u.password "foobar123"
    u.password_confirmation "foobar123"
    u.city "Madison"
    u.state "WI"
    u.zip_code "53726"
    u.date_of_birth "23/11/1989"
  end
end

reviews_controller.rb

def update
  @skills = @user.skills
  if @review.update(review_params)
    redirect_to @user, notice: 'Review was successfully updated.'
  else
    render :edit
  end
end

review.rb

class Review < ActiveRecord::Base
  has_one :reviewer, class_name: 'User', foreign_key: "reviewer_id"
  has_one :reviewee, class_name: 'User', foreign_key: "reviewww_id"
  belongs_to :skill

  validate :user_cannot_write_review_about_themselves, on: :create

  validates_presence_of :stars, :body, :reviewer_id, :reviewee_id, :skill_id

  def user_cannot_write_review_about_themselves
    if reviewer_id == reviewee_id
      errors.add(:reviewer, "cannot write a review about yourself")
    end
  end
end

This code keeps me giving the error:

Failure/Error: @review = FactoryGirl.create :review

ActiveRecord::RecordInvalid:

Validation failed: Reviewer cannot write a review about yourself, Reviewer can't be blank, Reviewee can't be blank

Please let me know if any other code snippets would also be required.