[Rails] 테스트: Minitest, RSpec, FactoryBot, Capybara

2026년 6월 20일 · 수정 2026년 6월 20일 · 📖 약 1분 · 348자/단어 #rails #testing #rspec #minitest #factory-bot

정의

Rails는 Minitest 기반 테스트를 기본 제공한다. 커뮤니티는 RSpec도 광범위 사용. FactoryBot(객체 생성), Capybara(브라우저 시뮬레이션), Rails System Test(통합)이 표준 도구. fixture와 factory 둘 다 사용 가능.

디렉터리 구조

test/                       # Minitest (Rails 기본)
    models/
    controllers/
    system/                 # E2E
    fixtures/
    test_helper.rb

spec/                       # RSpec
    models/
    controllers/
    requests/
    system/
    factories/
    rails_helper.rb

Minitest

# test/models/post_test.rb
require "test_helper"

class PostTest < ActiveSupport::TestCase
  test "presence of title" do
    post = Post.new(body: "...")
    assert_not post.valid?
    assert_includes post.errors[:title], "can't be blank"
  end

  test "creates a post" do
    assert_difference "Post.count", 1 do
      Post.create!(title: "Hi", body: "...")
    end
  end
end

bin/rails test                   # 전체
bin/rails test test/models       # 디렉터리
bin/rails test test/models/post_test.rb
bin/rails test test/models/post_test.rb:42    # 특정 라인

fixtures

# test/fixtures/posts.yml
hello:
  title: Hello
  body: World
  author: alice    # users.yml의 alice 참조
  created_at: <%= 1.day.ago %>

ruby_post:
  title: Ruby
  body: "..."

def setup
  @post = posts(:hello)
end

자동 로드. 빠르지만 데이터 변경 시 모든 테스트 영향.

FactoryBot

# Gemfile
gem "factory_bot_rails"

# spec/factories/posts.rb
FactoryBot.define do
  factory :post do
    title { "Test" }
    body { "Body" }
    association :author, factory: :user

    trait :published do
      published { true }
      published_at { Time.current }
    end

    trait :with_comments do
      after(:create) do |post|
        create_list(:comment, 3, post: post)
      end
    end
  end
end

사용:

post = create(:post)
posts = create_list(:post, 5)
published = create(:post, :published)
with_tags = build(:post, tags: [tag1, tag2])     # save X
attrs = attributes_for(:post)                     # hash

fixture보다 명시적·유연.

RSpec

gem "rspec-rails", group: [:development, :test]
bin/rails g rspec:install

# spec/models/post_spec.rb
require "rails_helper"

RSpec.describe Post, type: :model do
  describe "validations" do
    it { is_expected.to validate_presence_of(:title) }
    it { is_expected.to belong_to(:author) }
  end

  describe "#publish!" do
    let(:post) { create(:post) }

    it "marks as published" do
      post.publish!
      expect(post.published).to be true
      expect(post.published_at).to be_present
    end

    context "when already published" do
      let(:post) { create(:post, :published) }

      it "raises" do
        expect { post.publish! }.to raise_error(StandardError)
      end
    end
  end
end

bundle exec rspec
bundle exec rspec spec/models
bundle exec rspec spec/models/post_spec.rb:30

Controller / Request specs

# spec/requests/posts_spec.rb
RSpec.describe "Posts", type: :request do
  describe "GET /posts" do
    it "returns success" do
      get posts_path
      expect(response).to have_http_status(:ok)
    end
  end

  describe "POST /posts" do
    let(:user) { create(:user) }
    before { sign_in user }

    it "creates a post" do
      expect {
        post posts_path, params: { post: { title: "T", body: "B" } }
      }.to change(Post, :count).by(1)
      expect(response).to redirect_to(Post.last)
    end

    context "with invalid params" do
      it "renders new" do
        post posts_path, params: { post: { title: "" } }
        expect(response).to have_http_status(:unprocessable_entity)
      end
    end
  end
end

type: :request는 통합 테스트. controller spec(type: :controller)은 deprecated 방향.

System tests (browser)

# test/system/posts_test.rb
require "application_system_test_case"

class PostsTest < ApplicationSystemTestCase
  test "creating a post" do
    sign_in users(:alice)
    visit posts_path
    click_on "New post"
    fill_in "Title", with: "Hello"
    fill_in "Body", with: "World"
    click_on "Create Post"
    assert_text "Hello"
  end
end

Capybara 사용. Selenium/Cuprite 드라이버.

# test/application_system_test_case.rb
class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
  driven_by :selenium, using: :headless_chrome, screen_size: [1400, 1400]
end

또는 RSpec:

RSpec.describe "Posts", type: :system, js: true do
  before { driven_by :selenium, using: :headless_chrome }

  it "creates a post" do
    visit posts_path
    fill_in "Title", with: "Hi"
    click_button "Create"
    expect(page).to have_content "Hi"
  end
end

Mailer test

# spec/mailers/welcome_mailer_spec.rb
RSpec.describe WelcomeMailer, type: :mailer do
  describe "#welcome" do
    let(:user) { create(:user, email: "a@x.com") }
    let(:mail) { WelcomeMailer.welcome(user) }

    it "renders" do
      expect(mail.subject).to eq("환영합니다")
      expect(mail.to).to eq([user.email])
      expect(mail.body.encoded).to match("Hello")
    end
  end
end

테스트 환경 EMAIL: ActionMailer::Base.delivery_method = :test. ActionMailer::Base.deliveries에 mail 누적.

Job test

RSpec.describe SendWelcomeEmailJob, type: :job do
  let(:user) { create(:user) }

  it "enqueues" do
    expect {
      SendWelcomeEmailJob.perform_later(user.id)
    }.to have_enqueued_job(SendWelcomeEmailJob).with(user.id)
  end

  it "sends email" do
    expect {
      perform_enqueued_jobs do
        SendWelcomeEmailJob.perform_later(user.id)
      end
    }.to change { ActionMailer::Base.deliveries.size }.by(1)
  end
end

VCR (외부 API mock)

gem "vcr", group: :test

# spec/spec_helper.rb
VCR.configure do |c|
  c.cassette_library_dir = "spec/vcr_cassettes"
  c.hook_into :webmock
end

# 사용
RSpec.describe "API", :vcr do
  it "fetches data" do
    response = ApiClient.fetch_user(1)
    expect(response.name).to eq "Alice"
  end
end

첫 실행 시 실제 API 호출 → cassette 저장. 이후엔 cassette 재생.

DatabaseCleaner / 트랜잭션

RSpec은 기본 트랜잭션 wrapping (rollback). JS system test는 별도 thread → 트랜잭션 안 됨.

# spec/rails_helper.rb
RSpec.configure do |config|
  config.use_transactional_fixtures = true
  # JS 테스트엔 DatabaseCleaner truncation
end

shoulda-matchers

gem "shoulda-matchers"

RSpec.describe Post, type: :model do
  it { should validate_presence_of(:title) }
  it { should validate_uniqueness_of(:slug) }
  it { should belong_to(:author).class_name("User") }
  it { should have_many(:comments).dependent(:destroy) }
  it { should have_many(:tags).through(:post_tags) }
end

검증/관계를 한 줄로 테스트.

Mock / Stub

allow(User).to receive(:find).and_return(user)
expect(NotifyJob).to receive(:perform_later).with(user.id)

# instance
allow_any_instance_of(Post).to receive(:publish).and_return(true)

자주 보는 패턴

Request spec 표준

describe "PostsController" do
  describe "GET /posts" do
    let!(:posts) { create_list(:post, 3) }

    it "lists" do
      get posts_path
      expect(response).to be_successful
      expect(response.body).to include(posts.first.title)
    end
  end
end

Pundit policy spec

RSpec.describe PostPolicy do
  subject { described_class }

  permissions :update? do
    let(:user) { create(:user) }
    let(:post) { create(:post, author: user) }

    it "allows author" do
      expect(subject).to permit(user, post)
    end

    it "denies other" do
      other = create(:user)
      expect(subject).not_to permit(other, post)
    end
  end
end

Time travel

travel_to Time.zone.local(2026, 1, 1) do
  expect(Date.current).to eq(Date.new(2026, 1, 1))
end

# 또는 timecop
Timecop.freeze("2026-01-01")

함정

1. 트랜잭션과 background job

perform_enqueued_jobs 또는 inline adapter로 테스트 시 동기 실행.

2. system test flaky

비동기 처리, animation → 시간 대기 필요.

expect(page).to have_content("Saved", wait: 5)
# wait는 기본 2초

3. fixtures 순서

fixture 로드 순서가 보장 안 됨. ID 의존 코드 위험.

4. 너무 많은 stub

allow(...).to receive(...)
allow(...).to receive(...)
...

비즈니스 로직 결합 테스트가 됨. 통합 테스트가 가치 큼.

5. CI 느림

병렬 실행 (parallel_tests), --fail-fast, mock 줄이기.