Best way to test a mailer with arguments - ruby-on-rails

Question

I have a mailer that passes an argument like so:
AnimalMailer.daily_message(owner).deliver_later
The method looks like this:
AnimalMailer
class AnimalMailer < ApplicationMailer
def daily_message(owner)
mail(
to: "#{user.name}",
subject: "test",
content_type: "text/html",
date: Time.now.in_time_zone("Mountain Time (US & Canada)")
)
end
end
I'm new to writing specs and was wondering how should I pass the owner to the method and test it. I currently have this set up:
require "rails_helper"
RSpec.describe AnimalMailer, type: :mailer do
describe "monthly_animal_message" do
let(:user) { create(:user, :admin) }
it "renders the headers" do
expect(mail.subject).to eq("test")
expect(mail.to).to eq(user.name)
end
end
end

Answer 1

Specs generally follow a three-step flow 1) set up, 2) invoke, 3) expect. This applies for unit testing mailers like anything else. The invocation and parameters are the same in the test as for general use, so in your case:
RSpec.describe AnimalMailer, type: :mailer do
describe "monthly_campaign_report" do
let(:user) { create(:user, :admin) }
let(:mail) { described_class.daily_message(user) } # invocation
it 'renders the headers' do
expect(mail.subject).to eq('test')
expect(mail.to).to eq(user.name)
end
it 'renders the body' do
# whatever
end
end
end
Note that since the describe is the class name being tested, you can use described_class from there to refer back to the described class. You can always use AnimalMailer.daily_message as well, but among other things described_class ensures that if you shuffle or share examples that you are always testing what you think you are.
Also note that in the case of unit testing a mailer, you're mostly focused on the correct generation of the content. Testing of successful delivery or use in jobs, controllers, etc., would be done as part of request or feature tests.

Answer 2

Before testing it, make sure the config / environment / test.rb file is set to:
config.action_mailer.delivery_method = :test
This ensures that emails are not actually sent, but are stored in the ActionMailer :: Base.deliveries array.
Following Four-Phase Test :
animal_mailer.rb
class AnimalMailer < ApplicationMailer
default from: 'noreply#animal_mailer.com'
def daily_message(owner)
#name = owner.name
mail(
to: owner.email,
subject: "test",
content_type: "text/html",
date: Time.now.in_time_zone("Mountain Time (US & Canada)")
)
end
end
animal_mailer_spec.rb
RSpec.describe AnimalMailer, type: :mailer do
describe 'instructions' do
let(:user) { create(:user, :admin) }
let(:mail) { described_class.daily_message(user).deliver_now }
it 'renders the subject' do
expect(mail.subject).to eq("test")
end
it 'renders the receiver email' do
expect(mail.to).to eq([user.email])
end
it 'renders the sender email' do
expect(mail.from).to eq(['noreply#animal_mailer.com'])
end
it 'assigns #name' do
expect(mail.body.encoded).to match(user.name)
end
end
end
if you have a model user:
class User
def send_instructions
AnimalMailer.instructions(self).deliver_now
end
end
RSpec.describe User, type: :model do
subject { create :user }
it 'sends an email' do
expect { subject.send_instructions }
.to change { ActionMailer::Base.deliveries.count }.by(1)
end
end