Rails Testing Anti-Patterns (Confoo 2014)

Testing in our applications is essential to inspire confidence, catch regressions, and encourage simple designs. However, since tests have become such a large percentage of our applications, they're also prone to various code smells and anti-patterns. In this talk, we'll discuss various strategies to combat common testing mistakes found in Rails applications that reduce test code quality, performance, reliability, and maintainability.

Transcript

1. RAILS TESTING ANTI-PATTERNS by Kevin Faustino Confoo - February 28, 2014
2. Patterns found In The Wild
3. What is an Anti-Pattern? –Gerard Meszaros “A pattern that shouldn’t be used because it is known to produce less than optimal results.”
4. Slow Tests
5. http://xkcd.com/303/
6. Cause 
 Booting Rails on Every Test Run
7. Solution
 Use An Application Pre-Loader
8. Running Specs Without A Pre-Loader $ time bundle exec rspec --format progress!
10. Running Specs with Spring $ time bin/spring rspec spec --format progress!
11. Saves ~5 seconds each time you run your Test Suite
12. Integration with RSpec # Gemfile! ! group :development do! gem 'spring', '~> 1.1.0'! gem 'spring-commands-rspec', require: false! end!
13. Solution
 Isolate Rails From Your Tests
14. require 'spec_helper'! ! describe MailerPresenter do! describe '#sender_identifier' do! subject(:presenter) { MailerPresenter.new(sender, double(:recipient)) }! ! describe '#sender_identifier' do! context 'sender name not set' do! let(:sender) { double(:sender, name: nil, email: 'lex@lexcorp.com') }! ! it 'returns the email address of the sender' do! expect(presenter.sender_identifier).to eq(sender.email)! end! end! ! context 'sender name set' do! let(:sender) {! double(:sender, name: 'Lex Luthor', email: 'lex@lexcorp.com')! }! ! it 'returns name of sender' do! expect(presenter.sender_identifier).to eq(sender.name)! end! end! end! end! end!
15. class MailerPresenter! attr_reader :recipient, :sender! ! def initialize(sender, recipient)! @sender = sender! @recipient = recipient! end! ! def sender_identifier! sender.name || sender.email! end! end!
16. Running Spec $ time bundle exec rspec spec/presenters/mailer_presenter_spec.rb!
17. require_relative '../../app/presenters/mailer_presenter'! ! describe MailerPresenter do! describe '#sender_identifier' do! subject(:presenter) { MailerPresenter.new(sender, double(:recipient)) }! ! describe '#sender_identifier' do! context 'sender name not set' do! let(:sender) { double(:sender, name: nil, email: 'lex@lexcorp.com') }! ! it 'returns the email address of the sender' do! expect(presenter.sender_identifier).to eq(sender.email)! end! end! ! context 'sender name set' do! let(:sender) {! double(:sender, name: 'Lex Luthor', email: 'lex@lexcorp.com')! }! ! it 'returns name of sender' do! expect(presenter.sender_identifier).to eq(sender.name)! end! end! end! end! end!
18. Running Spec Without Rails $ time bundle exec rspec spec/presenters/mailer_presenter_spec.rb!
19. Cause 
 unnecessary Database Interaction
20. Solution
 Use Object Instances or
 Test Doubles
21. SPec That Creates A Record require 'spec_helper'! ! describe User do! describe '#full_name' do! subject(:user) {! User.create(first_name: 'Bruce', last_name: 'Wayne') ! }! ! it 'returns combined first name and last name of the user' do! expect(user.full_name).to eq('Bruce Wayne')! end! end! end!
23. SPec That Builds A Record require 'spec_helper'! ! describe User do! describe '#full_name' do! subject(:user) {! User.new(first_name: 'Bruce', last_name: 'Wayne') ! }! ! it 'returns combined first name and last name of the user' do! expect(user.full_name).to eq('Bruce Wayne')! end! end! end!
24. milliseconds Matter
25. .100 seconds X 100 Unit Tests = 10 seconds
26. The Obscure Test
27. Cause 
 The Eager Test
28. Verifies too much in a Single Test describe PostsController do! describe 'GET #show' do! let!(:post) { build_stubbed(:post) }! ! it 'gets show action' do! post_class = class_double('Post').as_stubbed_const! expect(post_class)! ! ! ! .to receive(:find).with(post.id).and_return(post)! ! ! ! get :show, id: post.id! expect(response.status).to eq(200)! expect(assigns(:post)).to eq(post)! expect(response).to render_template(:new)! end! end! end!
29. Solution
 Verify a single condition per Test
30. Verify a single condition per Test describe PostsController do! describe 'GET #show' do! let!(:post) { build_stubbed(:post) }! ! before do! post_class = class_double('Post').as_stubbed_const! expect(post_class).to receive(:find).with(post.id).and_return(post)! ! get :show, id: post.id! end! ! it 'renders the :show template' do! expect(response).to render_template(:new)! end! ! it 'assigns post' do! expect(assigns(:post)).to eq(post)! end! ! it 'returns success status' do! expect(response.status).to eq(200)! end! end! end!
31. Cause 
 The Mystery Guest
32. Test Reader is not able to see the cause and effect between the fixture and the verification logic
33. Prime Example: Fixtures
34. # users.yml! batman:! first_name: 'Bruce'! last_name: 'Wayne'! ! superman:! first_name: 'Clark'! last_name: 'Kent'!
35. require 'spec_helper'! ! describe User do! fixtures :users! ! describe '#full_name' do! subject(:user) { users(:superman) }! ! it 'returns combined first name and last name of the user' do! expect(user.full_name).to eq('Clark Kent')! end! end! end!
36. require 'spec_helper'! ! describe User do! fixtures :users! ! describe '#full_name' do! subject(:user) { users(:superman) }! ! it 'returns combined first name and last name of the user' do! expect(user.full_name).to eq('Clark Kent')! end! end! end!
37. Why Are Fixtures Are Bad?
38. Global When you include fixtures within your tests, They are made available to all your tests. ! This means every time you have to add a fixture to deal with an edge case, every other test has to deal with that new data point being part of the test data.
39. Spread Out Each model gets their own fixture file. If that fixture requires a connection to another fixture, you must manage that connection manually.
40. Brittle guaranteed to break any test that depends on the exact result of the model population. ! Example: Reports and Queries
41. Solution
 Use Factories
43. Factories are Local require 'spec_helper'! ! describe User do! describe '#full_name' do! subject(:user) do! ! build(:user, ! ! ! first_name: 'Clark', ! ! ! last_name: 'Kent') ! end! ! it 'returns combined first name and last name of the user' do! expect(user.full_name).to eq('Clark Kent')! end! end! end!
44. Create only the smallest amount of data needed to expose the issue in each test
45. The Bad Factory
46. Cause 
 The Empty factory
47. FactoryGirl.define do! !factory :user do! !end! end!
48. Solution
 Always Create Valid Factories
49. FactoryGirl.define do! factory :user do! name { Forgery(:name).full_name }! email { Forgery(:internet).email_address }! password { 'aBcdefg1' }! password_confirmation { password }! end! end!
50. Only have the fields necessary to create a valid object
51. Testing Your Factories # spec/support/factory_girl.rb! RSpec.configure do |config|! config.before(:suite) do! FactoryGirl.lint! end! end!
52. Cause 
 Not Handling Uniqueness
53. # app/models/user.rb! class User < ActiveRecord::Base! validates :email, uniqueness: true! end! # spec/factories/users.rb! FactoryGirl.define do! factory :user do! email 'user@example.com'! password 'abcdefg'! end! end!
54. Solution
 Use Sequences
55. FactoryGirl.define do! factory :user do! sequence(:email) {|n| "user#{n}@example.com" }! password 'abcdefg'! end! end!
56. The Erratic Test
57. Tests behave erratically. ! Sometimes They Pass, Sometimes they Fail!
58. Questions to Ask Which Environment did they fail on? CI or Local? Which Machine? ! What time did they fail at? Time Related? ! Do the Tests depend on any external Resources? Were they Available?
59. Solution
 Eliminate External Resources
60. Time
63. Timecop it 'freezes time' do! time = Time.local(2014, 2, 28, 10, 0, 0)! Timecop.freeze(time)! sleep(10)! expect(Time.current).to eq(time)! end! ! it 'travels back in time' do! time = Time.local(1955, 11, 5, 10, 0, 0)! Timecop.travel(time)! expect(Time.current).to eq(time)! end!
64. External HTTP Requests
66. Webmock stub_request(:get, “www.example.com")! .to_return(body: "abc", status: 200)!
67. Prevent Any External HTTP Request # spec/support/webmock.rb! require 'webmock/rspec'! ! RSpec.configure do |config|! config.before(:each) do! WebMock.reset!! WebMock.disable_net_connect!! end! end!
68. Redis
70. Use In-Memory Version of Redis require "fakeredis"! ! redis = Redis.new! ! >> redis.set "foo", "bar"! => "OK"! ! >> redis.get "foo"! => "bar"!
71. Stripe
73. Mock Calls to Stripe it "mocks a declined card error" do! # Prepares an error for the next create charge request! StripeMock.prepare_card_error(:card_declined)! ! expect { Stripe::Charge.create }.to raise_error {|e|! expect(e).to be_a Stripe::CardError! expect(e.http_status).to eq(402)! expect(e.code).to eq('card_declined')! }! end!
74. Bad Cukes
75. Cause 
 Incidental Details
76. Too much detail Feature: Signing In
 Background:! ! Given I am not authenticated
 Scenario: Successful Login! ! Given 1 user! ! And I go to the sign in page ! ! When I fill in "Email" with "bruce@wayneenterprises.com"! ! And I fill in "Password" with "batman"! ! And I press "Sign in"! ! Then I should be on the dashboard path! ! And I should see "Signed in successfully."!
77. Solution
 Use Declarative Style
78. Avoid Implementation Specifics Scenario: Successful Login! ! Given a user exists! ! When I sign in! ! Then I should be shown the dashboard!
79. Best Solution
 Avoid Cucumber
80. Use Capybara-RSpec require 'spec_helper'! ! feature 'User sign in' do! let!(:user) { create(:user) }! ! scenario 'allows a user to sign in after they have registered' do! sign_in_with(user)! ! expect(page).to have_flash_notice('Signed in successfully.')! end! end!
81. Write intention Revealing Helpers module Features! module SessionSteps! rspec type: :feature! ! def sign_in_form! find('.session form')! end! ! def sign_in_with(user)! ensure_on(new_user_session_path)! within(sign_in_form) do! fill_in('Email', with: user.email)! fill_in('Password', with: user.password)! click_button('Sign In')! end! end! end! end!
82. Mocking Without honouring The Contract
83. Mocks and Stubs are not enough class User < Struct.new(:notifier)! def suspend!! notifier.notify("suspended as")! end! end! ! describe User, '#suspend!' do! it 'notifies the console' do! notifier = double("ConsoleNotifier")! ! expect(notifier).to receive(:notify).with("suspended as")! ! user = User.new(notifier)! user.suspend!! end! end! http://rhnh.net/2013/12/10/new-in-rspec-3-verifying-doubles
84. actual method notify! Not Notify # console_notifier.rb! class ConsoleNotifier! def notify!(msg)! puts msg! end! end!
85. Spec still passes
86. Solution
 Use verifying Doubles
87. Using instance_double describe User, '#suspend!' do! it 'notifies the console' do! notifier = instance_double("ConsoleNotifier")! ! expect(notifier).to receive(:notify).with("suspended as")! ! user = User.new(notifier)! user.suspend!! end! end!
88. Interface Verification!
89. Available with RSpec Mocks instance_double - Creates a verifying double to be used for object instances ! class_double - Creates a verifying double for class methods and modules ! object_double - Create a verifying double from an existing object ! ! !
90. Production Bugs
91. We are finding too many bugs slipping into Production
92. Cause 
 Lack of Controller Tests
93. When Acceptance Testing with Cucumber/Capybara took off, Many developers abandoned controller specs altogether
94. Acceptance Tests covering every single possible controller code path is OVERKILL And Slow
95. Solution
 Write Controller Specs
96. Great For verifying web request successful? ! verifying correctly redirected to the right page? ! verifying a User was successfully authenticated? ! verifying The correct object stored in the response template? ! verifying the appropriate Flash message displayed to the user in the view?
97. A controller is a 
 class with methods 
 It should have tests! http://solnic.eu/2012/02/02/yes-you-should-write-controller-tests.html
98. Cause 
 No JavaScript Testing
99. JavaScript is becoming a very large part of our applications
100. Having 100% code coverage without testing JavaScript is a lie!
101. Solution
 Use teaspoon
103. Developers Not Writing Tests
104. Don’t Mortgage Your Future
105. why Test Instant Feedback Improved Code Quality Better Designed Code Confidence
106. Next Steps
107. Read These Books
108. Questions?