Testing mailers with Rspec and factory_bot

Question

• Hey guys, i need help, am new to testing and am testing my mailer but i do not understand y am getting this error when i run my tests.
• 'expected ActionMailer::Base.deliveries.size to have changed by 1, but was changed by 2'
• The emails are triggered by the after_create hook
• My code is working as expected but the tests are failing. Anyone with help is appreciated.

verfiy_mailer.rb

# frozen_string_literal: true

class VerifyMailer < ApplicationMailer
  def verification_email(user)
    @user = user
    mail(to: user.email, subject: 'verification code')
  end
end

verify_mailer_spec.rb

# frozen_string_literal: true

require 'rails_helper'
# include ActiveJob::TestHelper

RSpec.describe VerifyMailer, type: :mailer do
  let(:user) { create(:user) }
  let(:mail) { VerifyMailer.verification_email(user).deliver_now }

  it 'renders the receiver email' do
    expect(mail.to).to eq([user.email])
  end
  it 'renders the subject' do
    expect(mail.subject).to eq('verification code')
  end
  it 'renders the sender email' do
    expect(mail.from).to eq(['[email protected]'])
  end
end

user.rb

# frozen_string_literal: true

class User < ApplicationRecord
  after_create :send_user_otp
  attr_writer :login

  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable ,

  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :validatable, authentication_keys: [:username]
  has_many :payments
  validates :email, :username, presence: true, uniqueness: true
  validates :username, format: { with: /\A[a-zA-Z0-9_.]*\z/,
                                 message: ' only allow letter, number, underscore and punctuation marks' }

  # Loggin with user_name
  def login
    @login || username
  end

  def send_user_otp
    unverify!
    otp = generate_codes
    update_column(:otp_code, otp)
    VerifyMailer.verification_email(self).deliver_now
    touch(:otp_sent_at)
  end

  def unverify!
    update_column(:verified, false)
  end

  def generate_codes
    loop do
      code = rand(0o00000..999_999).to_s
      break code unless code.length != 6
    end
  end
end

• I have added config.action_mailer.delivery_method = :test to enviroment/test.rb

• am also using factory_bot_rails to create user

FactoryBot.define do
  factory :user do
    sequence(:email) { |n| "person#{n}@example.com" }
    sequence(:username) { |n| "user#{n}" }
    password { '!Mutebi2' }
    password_confirmation { '!Mutebi2' }
  end
end

Answer 1

As in most cases, the computer is doing exactly what you told it to do:

  let(:user) { create(:user) }
  let(:mail) { VerifyMailer.verification_email(user).deliver_now }

Creating the user with FactoryBot triggers any/all callbacks:

class User < ApplicationRecord
  after_create :send_user_otp

So create(:user) calls :send_user_otp after it's created.

Then you send another email with VerifyMailer.verification_email(user).deliver_now

Hence why ActionMailer::Base.deliveries.size changes by 2.

---

In your VerifyMailer tests, you are testing the attributes of the email, so you don't need the user to actually be saved or the email to actually be sent.

If you need an instance of the email, just remove deliver_now. And you can build instead of create the user:

RSpec.describe VerifyMailer, type: :mailer do
  let(:user) { build(:user) }
  let(:mail) { VerifyMailer.verification_email(user) }

  it 'renders the receiver email' do
    expect(mail.to).to eq([user.email])
  end
  it 'renders the subject' do
    expect(mail.subject).to eq('verification code')
  end
  it 'renders the sender email' do
    expect(mail.from).to eq(['[email protected]'])
  end
end

In your User tests, you can verify that creating a user also creates the email:

RSpec.describe User, type: :model do
  let(:user) { build(:user) }

  describe "after create" do
    it "calls #send_user_otp" do
      expect(user).to receive(:send_user_otp)
    end
  end

  describe "#send_user_otp" do
    it "calls VerifyMailer.verification_email" do
      expect(VerifyMailer).to receive(:verification_email).with(user)

      user.send(:send_user_otp)
    end
  end
end

Note that I'm not actually testing ActionMailer::Base.deliveries.size at all. That's a service or request test, which should be based on a full implementation, e.g.:

When this form is filled out:

• A User record gets created
• An email gets sent <= here is where you test that the email queue got an email

Your User model isn't responsible for VerifyMailer, ApplicationMailer and any other code that handles delver_now, it's only responsible for calling VerifyMailer and handing it the user instance.

And VerifyMailer isn't responsible for handling delivery, it creates the email and passes it off to ActionMailer.

Keep your tests focused on the responsibilities of your code, it will make them less brittle.

If you change something in your ActionMailer setup, you don't want User tests to start to fail.