'let' doesn't memoize values in rsepc - ruby-on-rails

Question

I have a user model, who have a many-to-many relationship whit itself: user A add user B as a friend, and automatically, user B becomes friend of user A too.
Performing the following steps in the rails console:
1) Create two users and save them:
2.3.1 :002 > u1 = User.new(name: "u1", email: "u1#mail.com")
=> #<User _id: 5788eae90640fd10cc85f291, created_at: nil, updated_at: nil, friend_ids: nil, name: "u1", email: "u1#mail.com">
2.3.1 :003 > u1.save
=> true
2.3.1 :004 > u2 = User.new(name: "u2", email: "u2#mail.com")
=> #<User _id: 5788eaf80640fd10cc85f292, created_at: nil, updated_at: nil, friend_ids: nil, name: "u2", email: "u2#mail.com">
2.3.1 :005 > u2.save
=> true
2) Add user u2 as friend of u1:
2.3.1 :006 > u1.add_friend u2
=> [#<User _id: 5788eaf80640fd10cc85f292, created_at: 2016-07-15 13:54:04 UTC, updated_at: 2016-07-15 13:55:19 UTC, friend_ids: [BSON::ObjectId('5788eae90640fd10cc85f291')], name: "u2", email: "u2#mail.com">]
3) Check their friendship:
2.3.1 :007 > u1.friend? u2
=> true
2.3.1 :008 > u2.friend? u1
=> true
As we can see, the "mutual friendship" works. But in my tests that doesn't happen. Here are my tests:
require 'rails_helper'
RSpec.describe User, type: :model do
let(:user) { create(:user) }
let(:other_user) { create(:user) }
context "when add a friend" do
it "should put him in friend's list" do
user.add_friend(other_user)
expect(user.friend? other_user).to be_truthy
end
it "should create a friendship" do
expect(other_user.friend? user).to be_truthy
end
end
end
Here are the tests result:
Failed examples:
rspec ./spec/models/user_spec.rb:33 # User when add a friend should create a friendship
The only reason that I can see to the second test is failing is because my let is not memoizing the association to use in other tests. What am I doing wrong?
Here is my User model, for reference:
class User
include Mongoid::Document
include Mongoid::Timestamps
has_many :posts
has_and_belongs_to_many :friends, class_name: "User",
inverse_of: :friends, dependent: :nullify
field :name, type: String
field :email, type: String
validates :name, presence: true
validates :email, presence: true
index({ email: 1 })
def friend?(user)
friends.include?(user)
end
def add_friend(user)
friends << user
end
def remove_friend(user)
friends.delete(user)
end
end

Answer 1

You need to move the creation of the relationship into a before block:
context "when add a friend" do
before do
user.add_friend(other_user)
end
it "should put him in friend's list" do
expect(user.friend? other_user).to be_truthy
end
it "should create a friendship" do
expect(other_user.friend? user).to be_truthy
end
end
In your code, you are only running it within the first it block, to the second one starts from scratch and it's not run.
With the before block, it is run once before each of the it blocks, so the spec should pass then.