Rails: Uninitialized constant User::VALID_EMAIL_REGEX - ruby

Question

Background - I am working with rails version 5.1.2. I am using Cloud 9 IDE. My problem relates to Ch 11 Rails Tutorial by Michael Hartl.
Problem details - typing $ rails test:mailers:
Error:
UserMailerTest#test_account_activation:
NameError: uninitialized constant User::VALID_EMAIL_REGEX
app/models/user.rb:6:in <class:User>'
app/models/user.rb:1:in'
bin/rails test test/mailers/user_mailer_test.rb:5
app/models/user.rb:1 - app/models/user.rb:6:
class User < ApplicationRecord
attr_accessor :remember_token, :activation_token
before_save :downcase_email
before_create :create_activation_digest
validates :email, presence: true, length: { maximum: 255 },
format: { with: VALID_EMAIL_REGEX },
uniqueness: { case_sensitive: false }
has_secure_password
validates :password, presence: true, length: { minimum: 6 }, allow_nil: true

Answer 1

Looks like you are missing the regex in your User model
class User < ApplicationsRecord
VALID_EMAIL_REGEX = /\A[\w+\-.]+#[a-z\d\-.]+\.[a-z]+\z/i
...
end

Answer 2

Just to add to Antarr Byrd's answer.
I had a similar experience when working on a Rails Application.
The issue was that I was defining the REGEX constant below the point of validation call.
That is, instead of this:
class User < ApplicationRecord
validates :email, presence: true, length: { maximum: 255 },
format: { with: VALID_EMAIL_REGEX }
VALID_EMAIL_REGEX = /\A[\w+\-.]+#[a-z\d\-.]+\.[a-z]+\z/i
end
Do this rather:
class User < ApplicationRecord
VALID_EMAIL_REGEX = /\A[\w+\-.]+#[a-z\d\-.]+\.[a-z]+\z/i
validates :email, presence: true, length: { maximum: 255 },
format: { with: VALID_EMAIL_REGEX }
end
That's all.
I hope this helps