Test Doubles

RSpec Test Doubles

RSpec instance_double - https://relishapp.com/rspec/rspec-mocks/v/3-10/docs/verifying-doubles/using-an-instance-double

RSpec spies - https://relishapp.com/rspec/rspec-mocks/v/3-10/docs/basics/spies

A Closer Look at Test Spies - https://thoughtbot.com/blog/a-closer-look-at-test-spies

RSpec allowing messages - https://relishapp.com/rspec/rspec-mocks/docs/basics/allowing-messages

Transcript

1. T st ou le 1
2. C ea in a ou le double("my double") 2
3. U in a ou le RSpec.describe "Book" do describe "#title" do it "stands in for a real object" do book_double = double("book", title: "Whale Sounds, Volume I") book_double.title expect(book_double.title).to eq("Whale Sounds, Volume I") end end end 3
4. C ll ng n nk ow m th d RSpec.describe “Book” do describe “#title” do it “stands in for a real object” do book_double = double(“book”, title: “Whale Sounds, Volume I”) book_double.method_that_does_not_exist # => <Double “book’> received unexpected message :method_that_does_not_exist end end end 4
5. I st nc d ub es class Book def title end end RSpec.describe “Book” do describe “#title” do it “stands in for a real object” do invalid_book_double = instance_double("Book", description: "") # => the Book class does not implement the instance method: description end end end 5
6. L t's om ar double 4 c o a s p a o 4 c d n m h s o 4 e : double("book", title: "") 6
7. L t's om ar i st nc _d ub e 4 e h d n m m h a o u s 4 e : instance_double(Book, title: "") 4 e : instance_double("Book", title: "") 7
8. L t's od ! 8
9. W at s he oa o o r es ? 9
10. U in a es D ub e o oc s ur es class Book attr_reader :title def initialize(title:) @title = title end end RSpec.describe BestSellerTitle do describe "#title" do it "prepends title with 'best seller'" do books = [Book.new(title: "Whale Songs")] title = BestSellerTitle.new.title(book) expect(title).to eq("Best Seller: Whale Songs") end end end 1
11. U in a es D ub e o oc s ur es RSpec.describe BestSellerTitle do describe "#title" do it "prepends title with 'best seller'" do book_double = instance_double(Book, title: "Whale Songs") title = BestSellerTitle.new.title(book_double) expect(title).to eq("Best Seller: Whale Songs") end end end 1
12. T st ng b ok c nt ol er RSpec.describe BooksController do describe "#index" do it "returns 10 published books" do books = FactoryBot.create_list(:book, 10, published: true ) FactoryBot.create(:book, published: false) get :index expect(assigns[:books]).to match_array(books) end end end 1
14. H w o e oc s hi t st? 1
15. allowi g eh vi r book = FactoryBot.build_stubbed(:book) allow(Book).to receive(:latest_published).and_return(book) 1
16. S ub in o r oo c as RSpec.describe BooksController do describe "#index" do it "returns 10 published books" do books = FactoryBot.build_list(:book, 2) allow(Book).to receive(:latest_published).and_return(books) get :index expect(assigns[:books]).to eq(books) end end end 1
17. RSpec.describe BooksController do describe "#index" do it "returns 10 published books" do books = FactoryBot.build_list(:book, 2) allow(Book).to receive(:latest_published).and_return(books) get :index expect(assigns[:books]).to eq(books) end end end 1
18. RSpec.describe BooksController do describe "#index" do it "returns 10 published books" do books = FactoryBot.build_list(:book, 2) allow(Book).to receive(:latest_published).and_return(books) get :index expect(assigns[:books]).to eq(books) end end end 1
19. RSpec.describe BooksController do describe "#index" do it "returns 10 published books" do books = FactoryBot.build_list(:book, 2) allow(Book).to receive(:latest_published).and_return(books) get :index expect(assigns[:books]).to eq(books) end end end 1
20. RSpec.describe BooksController do describe "#index" do it "returns 10 published books" do books = FactoryBot.build_list(:book, 2) allow(Book).to receive(:latest_published).and_return(books) get :index expect(assigns[:books]).to eq(books) end end end 2
21. L t's od ! 2
22. B t ha a e e es in ? 2
24. T st ng rg me ts # books_controller.rb Book.limit(per_page) # books_controller_spec.rb RSpec.describe BooksController do describe "#index" do it "finds the 10 latest published books" do books = FactoryBot.build_list(:book, 10) allow(Book).to receive(:limit).and_return(books) get :index expect(assigns[:books]).to eq(books) end end end 2
25. T st ng rg me ts # books_controller.rb Book.limit(per_page) # books_controller_spec.rb RSpec.describe BooksController do describe "#index" do it "finds the 10 latest published books" do books = FactoryBot.build_list(:book, 10) allow(Book).to receive(:limit).with(10).and_return(books) get :index expect(assigns[:books]).to eq(books) end end end 2
26. Q er a d om an m th ds 2
27. Q er m th ds A k q es io 4 W h u 's n ? 4 array.empty? 4 string.length 4 user.email 2
28. C mm nd et od H ve id e e ts 4 U h u 's e ! 4 user.save! 4 array.push 4 book.update_attributes 2
29. S ub in q er m th ds describe Signup do context "email" do it "delegates to the user" do user_double = instance_double("User", email: "user@example.com") signup = Signup.new(user: user_double) expect(signup.email).to eq(user.email) end end end 2
30. S ub in c mm nd et od describe Signup do context "#complete" do it "verifies the user's account" do user = instance_double("User") allow(user).to receive(:verify) signup = Signup.new(user: user) signup.complete(email: "new_user@example.com") end end end 3
31. S ub in c mm nd et od describe Signup do context "#complete" do it "calls verify on the user" do user = instance_double("User") allow(user).to receive(:verify) signup = Signup.new(user: user) signup.complete(email: "new_user@example.com") end end end 3
32. S ub in c mm nd et od describe Signup do context "#complete" do it "calls verify on the user" do user = instance_double("User") expect(user).to receive(:verify).with(email: "new_user@example.com") signup = Signup.new(user: user) signup.complete(email: "new_user@example.com") end end end 3
33. S ub in c mm nd et od describe Signup do context "#complete" do it "calls verify on the user" do user = instance_double("User") expect(user).to receive(:verify).with(email: "new_user@example.com") signup = Signup.new(user: user) signup.complete(email: "new_user@example.com") end end end 3
34. S ub in c mm nd et od describe Signup do context "#complete" do it "calls verify on the user" do user = instance_double("User") expect(user).to receive(:verify).with(email: "new_user@example.com") signup = Signup.new(user: user) signup.complete(email: "new_user@example.com") end end end 3
35. S ub in c mm nd et od describe Signup do context "#complete" do it "calls verify on the user" do user = instance_double("User") expect(user).to receive(:verify).with(email: "new_user@example.com") signup = Signup.new(user: user) signup.complete(email: "new_user@example.com") end end end 3
36. S ub in c mm nd et od describe Signup do context "#complete" do it "calls verify on the user" do user = instance_double("User") expect(user).to receive(:verify).with(email: "new_user@example.com") signup = Signup.new(user: user) signup.complete(email: "new_user@example.com") end end end 3
37. O de p ea e! describe Signup do context "#complete" do it "calls verify on the user" do # Setup user = instance_double("User") signup = Signup.new(user: user) # Setup and also verification??? expect(user).to receive(:verify).with(email: new_user@example.com) # Exercise signup.complete(email: "new_user@example.com") end end end 3
38. S ub in c mm nd et od describe Signup do context "#complete" do it "calls verify on the user" do # Setup user = instance_double("User") allow(user).to receive(:verify) signup = Signup.new(user: user) # Exercise signup.complete(email: "new_user@example.com") # Verify expect(user).to have_received(:verify).with(email: new_user@example.com) end end end 3
39. S ub in c mm nd et od describe Signup do context "#complete" do it "calls verify on the user" do # Setup user = instance_double("User") allow(user).to receive(:verify) signup = Signup.new(user: user) # Exercise signup.complete(email: "new_user@example.com") # Verify expect(user).to have_received(:verify).with(email: new_user@example.com) end end end 3
40. S ub in c mm nd et od describe Signup do context "#complete" do it "calls verify on the user" do # Setup user = instance_double("User") allow(user).to receive(:verify) signup = Signup.new(user: user) # Exercise signup.complete(email: "new_user@example.com") # Verify expect(user).to have_received(:verify).with(email: new_user@example.com) end end end 4
41. S ub in c mm nd et od describe Signup do context "#complete" do it "calls verify on the user" do # Setup user = instance_double("User") allow(user).to receive(:verify) signup = Signup.new(user: user) # Exercise signup.complete(email: "new_user@example.com") # Verify expect(user).to have_received(:verify).with(email: new_user@example.com) end end end 4
42. L t's od ! 4