add session mailer and spec

app/views/layouts/mailer.html.slim

@@ -0,0 +1,5 @@
+html xmlns="http://www.w3.org/1999/xhtml"
+  head
+    meta http-equiv="Content-Type" content="text/html; charset=utf-8"
+    meta name="viewport" content="width=device-width, initial-scale=1.0"
+  body lang=I18n.locale = yield

app/views/user_mailer/login_code.html.slim

@@ -0,0 +1 @@
+p Your login code is #{@code}

spec/support/mail_helper.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+class TestMail
+  attr_reader :to, :from, :subject, :body
+
+  def initialize(mail)
+    @to = mail["to"]
+    @from = mail["from"]
+    @subject = mail.subject
+    @original_body = mail.body.to_s
+    @body = Nokogiri::HTML(mail.body.to_s)
+  end
+
+  def link_urls
+    body.css("a").pluck("href")
+  end
+end
+
+module MailHelper
+  class NoMailSentError < StandardError; end
+
+  def last_mail
+    return nil unless ActionMailer::Base.deliveries.count > 0
+
+    TestMail.new(ActionMailer::Base.deliveries.last)
+  end
+
+  def last_mail!
+    last_mail || raise(NoMailSentError)
+  end
+
+  def reset_mails
+    ActionMailer::Base.deliveries = []
+  end
+
+  def run_jobs
+    # recursivly run the job queue until there are no jobs remaining
+    count = perform_enqueued_jobs
+    run_jobs if count.to_i > 0
+  end
+end
+
+RSpec.configure do |config|
+  config.before do
+    ActionMailer::Base.deliveries = []
+  end
+  config.include MailHelper, type: :system
+  config.include MailHelper, type: :model
+end

spec/system/session_spec.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require "system_helper"
+
+RSpec.describe "Sessions" do
+  fixtures :all
+
+  it "logs a user in via a code" do
+    visit root_path
+    expect(page).to have_content "Login"
+    fill_in "Email", with: "[email protected]"
+    click_on "Login"
+    expect(page).to have_content "Code"
+
+    run_jobs
+    expect(last_mail!.body).to have_content "Your login code is"
+    code = last_mail.body.to_s.scan(/\d{6}/).first
+    expect(code).to be_present
+    fill_in "Code", with: code
+    click_on "Login"
+    expect(page).to have_content "Hello"
+  end
+
+  it "logs the user out" do
+    login :john
+    visit logout_path
+    expect(page).to have_content "Login"
+  end
+end