Using Factories (or not)

Using Factories via FactoryBot

Transcript

1. Using factories (or not) 1
2. Why use factories? 2
3. Set up only the information you need. 3
4. TMI describe "#full_title" do it "combines the title and subtitle" do book = Book.new(title: "POODR", subtitle: "An Agile Primer", publication_year: 2012) expect(book.full_title).to eq "POODR: An Agile Primer" end end 4
5. TMI describe "#full_title" do it "combines the title and subtitle" do book = Book.new(title: "POODR", subtitle: "An Agile Primer", publication_year: 2012) expect(book.full_title).to eq "POODR: An Agile Primer" end end 5
6. Too little info describe "#full_title" do it "combines the title and subtitle" do expect(example_book.full_title).to eq "POODR: An Agile Primer" end end 6
7. Just Right describe "#full_title" do it "combines the title and subtitle" do book = Book.new(title: "POODR", subtitle: "An Agile Primer") expect(book.full_title).to eq "POODR: An Agile Primer" end end 7
8. Handling required fields class Book < ApplicationRecord validates :title, presence: true validates :subtitle, presence: true validates :publication_year, presence: true end describe "#full_title" do it "combines the title and subtitle" do # Invalid book = Book.new(title: "POODR", subtitle: "An Agile Primer") expect(book.full_title).to eq "POODR: An Agile Primer" end end 8
9. Enter the factory method pattern • Minimize mystery guests • Include all data that impacts expectation • Include no data that doesn't impact expectation # books_factory.rb factory :book do title { "default" } subtitle { "default" } publication_year { 2018 } end # book_spec.rb it "has a publication year" do book = FactoryBot.build_stubbed( :book, title: "POODR", subtitle: "An Agile Primer" ) expect(book.publication_year).to eq 2018 end 9
10. Why not use factories? • Easy to hide slow operations • Changes to factories have cascading effects • It can be slower than building an object directly # books_factory.rb factory :book do title { "default" } subtitle { "default" } publication_year { 2018 } author end factory :author 10
11. Questions to ask when building test data 11
12. Do I need a factory? • Do I need the db? • Do I need associations? • Do I need a lot of data to test this operation? If not, I might not need a factory. describe "#full_title" do it "combines the title and subtitle" do book = Book.new(title: "POODR", subtitle: "An Agile Primer") expect(book.full_title).to eq "POODR: An Agile Primer" end end 12
13. Which creation method do I need? • build • create • build_stubbed • attributes_for # Return an unsaved book instance book = build(:book) # Return a saved book instance book = create(:book) # return an object with all defined attributes stubbed out stub = build_stubbed(:book) # return a hash of attributes that can be used to build a book instance attributes = attributes_for(:book) 13
14. Which creation method do I need? • build • create • build_stubbed • attributes_for # Return an unsaved book instance book = build(:book) # Return a saved book instance book = create(:book) # return an object with all defined attributes stubbed out stub = build_stubbed(:book) # return a hash of attributes that can be used to build a book instance attributes = attributes_for(:book) 14
15. What info should I include in my factory? • As little as possible! • Mirror validations • Use traits for everything else 15
16. What info should I include in my factory? factory :author do name { "Chloe Ardelia Wofford" } pen_name { "Toni Morrison" } after(:create) do |author| create(:book, author: author) end end create(:author).pen_name # Toni Morrison create(:author).book.title # The Bluest Eye 16
17. What info should I include in my factory? factory :author do name { "Chloe Ardelia Wofford" } pen_name { "Toni Morrison" } after(:create) do |author| create(:book, author: author) end end create(:author).pen_name # Toni Morrison create(:author).book.title # The Bluest Eye 17
18. Named Factories Using Traits factory :author do name { "Chloe Ardelia Wofford" } trait :with_pen_name do pen_name { "Toni Morrison" } end trait :with_book do after(:create) do |author| create(:book, author: author) end end factory :author_with_pen_name, traits: [:with_pen_name] factory :author_with_book, traits: [:with_book] factory :author_with_pen_name_and_book, traits: [:with_pen_name, :with_book] end create(:author).pen_name # nil create(:author).book # nil create(:author_with_pen_name) # "Toni Morrison" create(:author_with_book).book.title # "The Bluest Eye" 18
19. Named Factories Using Traits factory :author do name { "Chloe Ardelia Wofford" } trait :with_pen_name do pen_name { "Toni Morrison" } end trait :with_book do after(:create) do |author| create(:book, author: author) end end factory :author_with_pen_name, traits: [:with_pen_name] factory :author_with_book, traits: [:with_book] factory :author_with_pen_name_and_book, traits: [:with_pen_name, :with_book] end create(:author).pen_name # nil create(:author).book # nil create(:author_with_pen_name) # "Toni Morrison" create(:author_with_book).book.title # "The Bluest Eye" 19
20. "Mixed-in" Traits factory :author do name { "Chloe Ardelia Wofford" } trait :with_pen_name do pen_name { "Toni Morrison" } end trait :with_book do after(:create) do |author| create(:book, author: author) end end end create(:author).pen_name # nil create(:author).book # nil create(:author, :with_pen_name).pen_name # "Toni Morrison" create(:author, :with_book).book.title # "The Bluest Eye" create(:author, :with_pen_name, :with_book).book.title # "The Bluest Eye" create(:author, :with_pen_name, :with_book).pen_name # "Toni Morrison" 20
21. "Mixed-in" Traits factory :author do name { "Chloe Ardelia Wofford" } trait :with_pen_name do pen_name { "Toni Morrison" } end trait :with_book do after(:create) do |author| create(:book, author: author) end end end create(:author).pen_name # nil create(:author).book # nil create(:author, :with_pen_name).pen_name # "Toni Morrison" create(:author, :with_book).book.title # "The Bluest Eye" create(:author, :with_pen_name, :with_book).book.title # "The Bluest Eye" create(:author, :with_pen_name, :with_book).pen_name # "Toni Morrison" 21
22. Resources Why Factories - https://thoughtbot.com/blog/why-factories Factories should be the bare minimum - https://thoughtbot.com/blog/factories- should-be-the-bare-minimum Speed up tests by selectively avoiding FactoryBot - https://thoughtbot.com/blog/speed-up-tests- by-selectively-avoiding-factory-girl Remove duplication with FactoryBot's traits - https://thoughtbot.com/blog/remove- duplication-with-factorygirls-traits 22