rails test makes Mysql2 complain about default value - ruby-on-rails-3

Question

I'm pretty confused about an error I get trying to unit test a model (User) I have.
I have a fixture for the model in test/fixtures/users.yml
new_user_in_unavailable_country:
first_name: John
last_name: Lennon
email: john.lennon#pop.co.uk
password: YokoOn0
country: UNITED KINGDOM
Now in test/unit/user_test.rb I have
require 'test_helper'
class UserTest < ActiveSupport::TestCase
test "status_auto_fill_for_unavailable_country" do
users(:new_user_in_unavailable_country).valid?
assert users(:new_user_in_unavailable_country).status == "SUBSCRIBED"
end
end
So far so good. Now, here is what that generates upon rake:test:units :
Error:
test_status_auto_fill_for_available_country(UserTest):
ActiveRecord::StatementInvalid: Mysql2::Error: Field 'name' doesn't have a default value: INSERT INTO `countries` (`id`) VALUES (980190962)
Okay, if there is an hidden insert somewhere into table countries (which I never asked for!), I should be able to see that upon running the same code in a rails console.
So I tried:
> usr = User.new(:first_name => "John", :last_name => "Lennon", :email => "john.lennon#pop.co.uk", :password => "YokoOn0", :country => "UNITED KINGDOM")
#<User id: nil, first_name: "John", last_name: "Lennon", email: "john.lennon#pop.co.uk", hashed_password: nil, password_salt: nil, created_at: nil, updated_at: nil, organization_id: nil, country: "UNITED KINGDOM", status: nil>
>> usr.valid?
(1.0ms) SELECT COUNT(*) FROM `countries` WHERE `countries`.`available` = 1 AND `countries`.`name` = 'UNITED KINGDOM'
(1.0ms) SELECT COUNT(*) FROM `countries` WHERE `countries`.`available` = 1 AND `countries`.`name` = 'UNITED KINGDOM'
(0.0ms) SELECT COUNT(*) FROM `countries` WHERE `countries`.`available` = 1 AND `countries`.`name` = 'UNITED KINGDOM'
(1.0ms) SELECT COUNT(*) FROM `countries` WHERE `countries`.`available` = 1 AND `countries`.`name` = 'UNITED KINGDOM'
(0.0ms) SELECT COUNT(*) FROM `countries` WHERE `countries`.`available` = 1 AND `countries`.`name` = 'UNITED KINGDOM'
(0.0ms) SELECT COUNT(*) FROM `countries` WHERE `countries`.`available` = 1 AND `countries`.`name` = 'UNITED KINGDOM'
(0.0ms) SELECT COUNT(*) FROM `countries` WHERE `countries`.`available` = 1 AND `countries`.`name` = 'UNITED KINGDOM'
(0.0ms) SELECT COUNT(*) FROM `countries` WHERE `countries`.`available` = 1 AND `countries`.`name` = 'UNITED KINGDOM'
(0.0ms) SELECT COUNT(*) FROM `countries` WHERE `countries`.`available` = 1 AND `countries`.`name` = 'UNITED KINGDOM'
User Exists (1.0ms) SELECT 1 FROM `users` WHERE `users`.`email` = BINARY 'john.lennon#pop.co.uk' LIMIT 1
true
>> usr.status
"SUBSCRIBED"
Okay, no insertion into countries table.
Anyidea of what happens behind the scene that I am missing and that generates this error?
Create Country migration:
class CreateCountries < ActiveRecord::Migration
def change
create_table :countries do |t|
t.string :name , :null => false
t.string :iso_2_letters_code , :null => false
t.string :iso_3_letters_code , :null => false
t.integer :phone_code
end
add_index :countries , :iso_2_letters_code , :unique => true
add_index :countries , :iso_3_letters_code , :unique => true
end
end