テスト方法

require 'rails_helper'

RSpec.feature "Users", type: :feature do
  scenario 'user deletes a user' do
    user = FactoryBot.create(:user)
    user.funds << FactoryBot.build(:fund)
    user.ratios << FactoryBot.build(:ratio)
    user.save

    visit root_path
    click_link 'ログイン'
    fill_in 'メールアドレス', with: user.email
    fill_in 'パスワード', with: user.password
    click_button 'ログイン'

    expect{
      click_button '削除'
      page.driver.browser.switch_to.alert.accept

      expect(page).to have_content '投資信託管理サービス'
    }.to change(User, :count).by(-1).and change(Fund, :count).by(-1).and change(Ratio, :count).by(-1)
  end
end

$ rspec spec/features

Users
Capybara starting Puma...
* Version 3.12.1 , codename: Llamas in Pajamas
* Min threads: 0, max threads: 4
* Listening on tcp://127.0.0.1:59581
  user deletes a user

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2 examples, 0 failures