Testing in Ruby

A quick-ish introduction to testing (in particular, in Ruby) for a guest lecture at the University of Western Australia.

Transcript

1. Testing in Ruby
2. I’m Darcy
3. Fellow student here
4. I make APIs for iOS Apps in Ruby
5. Q: What is testing?
6. Automated Testing
7. Verifiable contracts
8. Given this, I expect that.
9. “Test Suites”
10. Q: Why test?
11. Testing as a contract
12. Prevent regressions.
13. Verify your assumptions
14. Confirm you’re understanding
15. Things you forget.
16. Real World Example: Merging data.
17. Testing as a design tool
18. “T.D.D.”
19. Test-first development
20. Red Green Refactor
21. Write a failing test
22. require 'test_helper' class PersonTest < ActiveSupport::TestCase test "making a full name" do person = Person.new first_name: "Bob", last_name: "Smith" assert_equal "Bob Smith", person.full_name end end
23. # Running tests: E Finished tests in 0.057601s, 17.3608 tests/s, 0.0000 assertions/s. 1) Error: PersonTest#test_making_a_full_name: NoMethodError: undefined method `full_name' for #<Person:0x007fcc4e4dea50> test/models/person_test.rb:7:in `block in <class:PersonTest>' 1 tests, 0 assertions, 0 failures, 1 errors, 0 skips ==============================================================================
24. Make it pass
25. class Person < ActiveRecord::Base def full_name first_name + " " + last_name end end
26. # Running tests: . Finished tests in 0.132392s, 7.5533 tests/s, 7.5533 assertions/s. 1 tests, 1 assertions, 0 failures, 0 errors, 0 skips ==============================================================================
27. Refactor it.
28. class Person < ActiveRecord::Base def full_name "#{first_name} #{last_name}".strip end end
29. # Running tests: . Finished tests in 0.177100s, 5.6465 tests/s, 5.6465 assertions/s. 1 tests, 1 assertions, 0 failures, 0 errors, 0 skips ==============================================================================
30. We’re all human.
31. Work out what you want
32. Write as little as possible to make it happen
33. Work out what you don’t know
34. Testing as documentation
35. Testing in Rails
36. Rails <3’s testing
37. Testing is a standard part of Rails
38. $ rake
39. Run options: --seed 13019 # Running tests: ...FE Finished tests in 0.077580s, 64.4496 tests/s, 51.5597 assertions/s. 1) Failure: PersonTest#test_making_a_name_with_no_given_names [/Users/sutto/Code/test_project/test/models/person_test.rb:22]: Expected: nil Actual: "" 2) Error: PersonTest#test_making_searching_for_users: NoMethodError: undefined method `search' for #<Class:0x007fc835b1efe0> test/models/person_test.rb:28:in `block in <class:PersonTest>' 5 tests, 4 assertions, 1 failures, 1 errors, 0 skips ============================================================================== Run options: --seed 5103 # Running tests: . Finished tests in 0.086914s, 11.5056 tests/s, 11.5056 assertions/s. 1 tests, 1 assertions, 0 failures, 0 errors, 0 skips ==============================================================================
40. Generates automatically generate stubs for you.
41. xUnit
42. JUnit
43. Test::Unit
44. MiniTest
45. Assertions
46. assert <a boolean expression>
47. assert_equal 2, (1 + 1)
48. Unit / Model Tests
49. Small, independent bits of functionality.
50. Minimal set of dependencies
51. test "making a name with first and last name" do person = Person.new first_name: "Bob", last_name: "Smith" assert_equal "Bob Smith", person.full_name end test "making a name with first name only" do person = Person.new first_name: "Bob" assert_equal "Bob", person.full_name end test "making a name with last name only" do person = Person.new last_name: "Smith" assert_equal "Smith", person.full_name end test "making a name with no given names" do person = Person.new assert_equal nil, person.full_name end
52. Test edge cases
53. Small, fast and easy to test assumptions.
54. test "making searching for users" do person = Person.create! first_name: "Bob", last_name: "Smith" # Actually hit the database and get a result... Person.search('Bob Smith').should == [person] end
55. Functional / Controller Tests
56. Test how the model, view and controller interact
57. require 'test_helper' class PeopleControllerTest < ActionController::TestCase test "should list users" do person = Person.create! get :index assert_equal [person], assigns(:people) end end
58. test "redirecting when not logged in" do get :index assert_response :redirect assert_redirected_to some_other_page end test "visible when logged in" do get :index assert_response :success end
59. Guarantees*.
60. * Only test what you specify, nothing more.
61. Checks the glue.
62. Integration tests.
63. The bigger picture
64. E.g. user stories
65. User logs in, purchases an item, order is placed.
66. Slower to run, but test everything together.
67. Taking it Further
68. Full Stack Tests
69. Coverage Tools
70. Simplecov
72. See code that isn’t tested
73. BDD
74. RSpec
75. minitest-spec
76. What I’ve learnt about testing
77. Over testing is bad.
78. Slow tests sucks.
79. Testing should be instinctive
80. Don’t get stuck on numbers (coverage, number of tests)
81. Good tests inspire confidence
82. Only test what you implement
83. If you have to be told to test, it’s probably not going to help
84. It takes time to learn to write good tests
85. Don’t be afraid to write tests before code
86. Most importantly, writing tests costs less long term.