Test anti-patterns

Lightning talk presented in a small event at Aracaju - Sergipe

Transcript

1. Tests anti-patterns
2. Rafael França @rafaelfranca
3. Rails Core Member
4. Tests anti-patterns
5. Mystery Guest
6. The test reader is not able to see the cause and effect between fixture and verification logic because part of it is done outside the Test Method.
7. • A fixture • An instance variable defined far way from the test • A variable without a good name Sym ptom s
8. describe User do it 'can be a developer' do user = users(:rafael) expect(user).to be_developer end end Sym ptom s
9. describe User do let(:developer) { users(:developer) } ! context 'when it has GitHub account' do it 'bla bla bla' do ... end ! it 'bla bla bla' do ... end ! it 'bla bla bla' do ... end ! it 'is a developer' do expect(developer).to be_developer end end end Sym ptom s
10. describe User do context 'user account exists with a GitHub id' do before do @user = User.create(name: 'Foo', active: true, gh_user_id: 123456) end end end Sym ptom s
11. • Tests don’t have documentation role • Change to one test can break others Im pact
12. describe User do it 'can be a developer' do user = create(:user, role: 'developer') expect(user).to be_developer # assert_equal true, user.developer? end end Solution
13. describe User do context 'when it has GitHub account' do it 'bla bla bla' do ... end ! it 'bla bla bla' do ... end ! it 'bla bla bla' do ... end ! it 'is a developer' do developer = users(:developer) expect(developer).to be_developer end end end Solution
14. describe User do context 'user account exists with a GitHub id' do before do @user = create(:user, gh_user_id: 123456) end end end Solution
15. Stubbing the System Under Test
16. whatever class, object or method we are testing; when we are writing customer tests, the SUT is probably the entire application or at least a major subsystem of it.
17. Sym ptom s describe User do it 'gets the GitHub information' do user_information = ... expect(User).to( receive(:get_information).and_return(user_information) ) ! expect(User.find_by_id(user_uid)).to( eq(User.new(user_information)) ) end end
18. • Hard to test code Im pact
19. Solution describe User do it 'gets the GitHub information' do user_information = ... client = double('GitHub client') ! expect(client).to receive(:get).and_return(user_information) ! expect(User.find_by_id(client, user_uid)).to( eq(User.new(user_information)) ) end end
20. Developers not writing tests
21. We hear that our developers aren't writing tests
22. • Production Bugs Sym ptom s
23. • Loss of confidence • Take longer to add new features • Decrease of Refactoring and code improvements Im pact
24. • Talk with your team • Address the root causes • Not enough time • Hard to test code • Wrong test automation strategy • Write regression tests Solution
25. Only the happy path is tested
26. Thanks! Rafael França - @rafaelfranca
27. • http://robots.thoughtbot.com/mystery-guest • http://robots.thoughtbot.com/don-t-stub-the- system-under-test • http://xunitpatterns.com/