EmailAddress class with unit tests.

email_address.rb

require "i18n"

class EmailAddress
  VALID_EMAIL_ADDRESS_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i

  def self.malformed?(email)
    email !~ VALID_EMAIL_ADDRESS_REGEX
  end

  def self.valid?(email)
    !malformed?(email)
  end

  attr_reader :email, :i18n_scope, :errors

  def initialize(email, i18n_scope: [:models, :email_address])
    @email = email
    @i18n_scope = i18n_scope
    @errors = []
  end

  def valid?
    validate
    errors.empty?
  end

  def validate
    message = I18n.t(:invalid, scope: i18n_scope)
    errors.push(message) if EmailAddress.malformed?(email)
  end
end

email_address_test.rb

require 'test_helper'

class EmailAddressTest < ActiveSupport::TestCase
  valid_emails = ['homer@simp.sp', '_BART_@simp.com', 'lisa.simp@spring.field.com', 'marg+simp@spring.field']
  invalid_emails = ['homer@simp', '_BART_@ simp.com', 'lisa.simp.field.com', '@spring.com', 'lisa@', 'ba rt@simp.com']

  valid_emails.each do |email|
    test "email #{email} should be valid" do
      assert_match EmailAddress::VALID_EMAIL_ADDRESS_REGEX, email
    end
  end

  invalid_emails.each do |email|
    test "email #{email} should not be valid" do
      assert_no_match EmailAddress::VALID_EMAIL_ADDRESS_REGEX, email
    end
  end

  test "valid? returns true for valid email" do
    assert EmailAddress.valid?("milhouse@springville.com")
  end

  test "valid? returns false for invalid email" do
    refute EmailAddress.valid?("milhouse@springville")
  end

  test "#initialize sets email, i18n_scope, and errors instance variables" do
    email_address = EmailAddress.new("email@address.com", i18n_scope: [:models, :model])

    assert_includes email_address.instance_variables, :@email
    assert_includes email_address.instance_variables, :@i18n_scope
    assert_includes email_address.instance_variables, :@errors
  end

  test "#initialize can be called without i18n_scope" do
    assert_nothing_raised do
      EmailAddress.new("email@address.com")
    end
  end

  test "validate adds error for invalid email" do
    email_address = EmailAddress.new("email@address")
    email_address.validate
    assert_equal 1, email_address.errors.size
  end

  test "validate does not add error for valid emial" do
    email_address = EmailAddress.new("email@address.com")
    email_address.validate
    assert_equal 0, email_address.errors.size
  end
end