rails turorial 11章の11.2.2 送信メールのテストを通したい。

Question

前提・実現したいこと

現在rails tutorialで勉強中です。
rails turorial 11章の11.2.2 送信メールのプレビューのテストを通したいです。
■■な機能を実装中に以下のエラーメッセージが発生しました。

発生している問題・エラーメッセージ

テストに表示されているエラーです。

ERROR["test_account_activation", UserMailerTest, 0.3481637069999124]
 test_account_activation#UserMailerTest (0.35s)
ArgumentError:         ArgumentError: wrong number of arguments (given 0, expected 1)
            app/mailers/user_mailer.rb:8:in `account_activation'
            test/mailers/user_mailer_test.rb:6:in `block in <class:UserMailerTest>'

  1/1: [===================================] 100% Time: 00:00:00, Time: 00:00:00

Finished in 0.35140s
1 tests, 0 assertions, 0 failures, 1 errors, 0 skips

app/mailers/user_mailer.rb:8:in `account_activation'　このエラーコードから　account_activationに引数が期待している値というエラーだと思いました。以下に関係のありそうなコードを添付します。

該当のソースコード

app/mailers/user_mailer

class UserMailer < ApplicationMailer

  # Subject can be set in your I18n file at config/locales/en.yml
  # with the following lookup:
  #
  #   en.user_mailer.account_activation.subject
  #
  def account_activation(user)
    @user = user
    mail to: user.email, subject: "Account activation" #subjectキーは件名
  end

  # Subject can be set in your I18n file at config/locales/en.yml
  # with the following lookup:
  #
  #   en.user_mailer.password_reset.subject
  #
  def password_reset
    @greeting = "Hi"

    mail to: "[e-mail]"
  end
end

テストコードのです。

usesr_mailer_test.rb

require 'test_helper'

class UserMailerTest < ActionMailer::TestCase
  test "account_activation" do
    mail = UserMailer.account_activation
    assert_equal "Account activation", mail.subject
    assert_equal ["[e-mail]"], mail.to
    assert_equal ["[e-mail]"], mail.from
    assert_match user.name,               mail.body.encoded
    assert_match user.activation_token,   mail.body.encoded
    assert_match CGI.escape(user.email),  mail.body.encoded
  end


end

user_mailer_preview.rb

# Preview all emails at http://localhost:3000/rails/mailers/user_mailer
class UserMailerPreview < ActionMailer::Preview

  # Preview this email at http://localhost:3000/rails/mailers/user_mailer/account_activation
  def account_activation
    user = User.first
    user.activation_token = User.new_token
    UserMailer.account_activation(user)
  end

  # Preview this email at http://localhost:3000/rails/mailers/user_mailer/password_reset
  def password_reset
    UserMailer.password_reset
  end

end

config/environments/test.rb

Rails.application.configure do
  # Settings specified here will take precedence over those in config/application.rb.

  # The test environment is used exclusively to run your application's
  # test suite. You never need to work with it otherwise. Remember that
  # your test database is "scratch space" for the test suite and is wiped
  # and recreated between test runs. Don't rely on the data there!
  config.cache_classes = true

  # Do not eager load code on boot. This avoids loading your whole application
  # just for the purpose of running a single test. If you are using a tool that
  # preloads Rails for running tests, you may have to set it to true.
  config.eager_load = false

  # Configure public file server for tests with Cache-Control for performance.
  config.public_file_server.enabled = true
  config.public_file_server.headers = {
    'Cache-Control' => "public, max-age=#{1.hour.seconds.to_i}"
  }

  # Show full error reports and disable caching.
  config.consider_all_requests_local       = true
  config.action_controller.perform_caching = false

  # Raise exceptions instead of rendering exception templates.
  config.action_dispatch.show_exceptions = false

  # Disable request forgery protection in test environment.
  config.action_controller.allow_forgery_protection = false
  config.action_mailer.perform_caching = false

  # Tell Action Mailer not to deliver emails to the real world.
  # The :test delivery method accumulates sent emails in the
  # ActionMailer::Base.deliveries array.
  config.action_mailer.delivery_method = :test
  config.action_mailer.default_url_options = { host: 'example.com' }
  # Print deprecation notices to the stderr.
  config.active_support.deprecation = :stderr

  # Raises error for missing translations
  # config.action_view.raise_on_missing_translations = true
  

end

上のコードを見るとaccount_activationには引数は与えられていると思うのですがなぜこのようなエラーが出ているのでしょうか？
雑な質問で申し訳ございませんが、解答のほどよろしくお願い致します。

Answer 1

テストコードを間違えていました。書き換えたら通りました。
正しくは以下のものです。

require 'test_helper'

class UserMailerTest < ActionMailer::TestCase

  test "account_activation" do
    user = users(:michael)
    user.activation_token = User.new_token
    mail = UserMailer.account_activation(user)
    assert_equal "Account activation", mail.subject
    assert_equal [user.email], mail.to
    assert_equal ["[e-mail]"], mail.from
    assert_match user.name,               mail.body.encoded
    assert_match user.activation_token,   mail.body.encoded
    assert_match CGI.escape(user.email),  mail.body.encoded
  end
end