Rails fixture doesn't recognize a belongs_to relationship

I have 2 models :

class User < ApplicationRecord
  has_many :games, dependent: :nullify

class Game < ApplicationRecord
  belongs_to :user
  belongs_to :playlist, optional: true

In my fixtures, game only belongs_to users. My only fixtures are :

user.yml

michel:
  id: 1
  pseudo: michelchardou
  email: mich@chardou.com
  encrypted_password: User.digest('password')
  admin: false

game.yml

game1:
  user: michel
  token: 123456
  total_score: 0

My basic tests work for

  test "should get expected game fixture token" do
    assert_equal '123456', @game1.token
    assert_equal 0, @game1.total_score
  end

but the following raises an error :

  test "should get expected game fixture user" do
    assert_equal 'michel', @game1.user
  end

the error is :

Failure:
GameTest#test_should_get_expected_game_fixture_user [/Users/pierre/code/pierregarciafr/wadzatsong/test/models/game_test.rb:25]:
Expected: "michel"
  Actual: nil

Why ?

That's because you're manually assigning the id your user (michel) is going to have, and you should leave that to Rails (or the ORM), try deleting that line.

The fixture for the user michel should be like:

michel:
  pseudo: michelchardou
  email: mich@chardou.com
  encrypted_password: User.digest('password')
  admin: false

In the other hand your first example works without problem because you're not testing the relationship between both models, you're checking what was explicitly added to the fixture file.