Add New Comment on your post notifications

This notification is sent only to the post owner, unless this person turned off the notifications.
A simple first step into the notifications by mail world :)

The mail contains a link to user profile
The link to the user profile is required to give an easy access to
notifications disabling.

Also having a preview for the notify_post_owner method

We can `Comment.first` because it is part of the db:seeds method. So
there should, in development, always be one.

spec/mailers/previews/user_mailer_preview.rb

@@ -0,0 +1,6 @@
+# Preview all emails at http://localhost:3000/rails/mailers/user_mailer
+class UserMailerPreview < ActionMailer::Preview
+  def notify_post_owner
+    UserMailer.notify_post_owner(comment: Comment.first)
+  end
+end

spec/mailers/user_mailer_spec.rb

@@ -0,0 +1,22 @@
+require "rails_helper"
+
+RSpec.describe UserMailer, type: :mailer do
+  describe "notify_comment" do
+    let(:user) { FactoryBot.create(:user, email: "notified@example.com", notifications_enabled: true) }
+    let(:post) { FactoryBot.create(:post, user: user)}
+    let(:comment) { FactoryBot.create(:comment, post: post) }
+    let(:mail) { UserMailer.notify_post_owner(comment: comment) }
+
+    it "renders the headers" do
+      expect(mail.subject).to eq("[#{ENV.fetch('APP_NAME')}] - New comment on #{post.title}")
+      expect(mail.to).to eq(["notified@example.com"])
+      expect(mail.from).to eq(["notifications@example.com"])
+    end
+
+    it "renders the body" do
+      expect(mail.body.encoded).to include("Hello, #{user.full_name}")
+      expect(mail.body.encoded).to include("There is a new comment by")
+      expect(mail.body.encoded).to include('Annoyed ? You can <a href="http://localhost:3000/users/edit">turn off notifications here</a>')
+    end
+  end
+end

spec/support/action_mailer.rb

@@ -0,0 +1,5 @@
+RSpec.configure do |config|
+  config.before(:each) do
+    ActionMailer::Base.deliveries.clear
+  end
+end

spec/system/comments_spec.rb

@@ -108,4 +108,34 @@ feature 'comments', type: :system, js: true do
 
     expect(Comment.where(post_id: post.id).count).to eq(comments_count + 1)
   end
-end
+
+  it 'notifies post owner when comment is posted' do
+    log_in_as user
+    visit post_path(post)
+    allow(UserMailer).to receive_message_chain(:notify_post_owner, :deliver_later)
+
+    comment_body = 'this is a comment!'
+
+    find(newCommentBodySelector).fill_in with: comment_body
+    click_button 'Submit'
+    visit post_path(post)
+
+    expect(UserMailer).to have_received(:notify_post_owner)
+  end
+
+  it 'does not notify the post owner if he refused notifications' do
+    post_owner = FactoryBot.create(:user, notifications_enabled: false)
+    post = FactoryBot.create(:post, user: post_owner)
+    log_in_as user
+    visit post_path(post)
+    allow(UserMailer).to receive_message_chain(:notify_post_owner, :deliver_later)
+
+    comment_body = 'this is a comment!'
+
+    find(newCommentBodySelector).fill_in with: comment_body
+    click_button 'Submit'
+    visit post_path(post)
+
+    expect(UserMailer).not_to have_received(:notify_post_owner)
+  end
+end

spec/system/user_sign_up_spec.rb

@@ -77,7 +77,7 @@ feature 'sign up', type: :system do
     expect(page).to have_css('.alert')
   end
 
-  scenario 'and disables notifications' do
+  scenario 'with disabled notifications' do
     visit new_user_registration_path
     fill_in 'Full name', with: user.full_name
     fill_in 'Email', with: user.email