Let your test drive your development.

#sprk2012 talk. Described 'why does test drive a development'.

Transcript

1. Let your test drive your development Kyosuke MOROHASHI
3. About me • MOROHASHI Kyosuke • @moro on Twitter and GitHub • works at @esminc • One of the authors of Rails3 Recipe Book
7. =begin PR about us
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15. =end
16. Let your test drive your development ςετʹ։ൃΛ ۦಈ͍ͤͨ͞
17. Agenda • Some may think that tests are interrupters of software development. • I think tests are good drivers of development.
18. Why write test? • Because it's RIGHT way. • Because it improves QUALITY. • Because it reports regression early. -- Is it only an expensive insurance for the future?
19. http://flic.kr/p/zBdU7 Test drives Development It's not only skill, manner or RIGHT way but simply a driver for programming.
20. think code run What we do when we code? Programming workflow
21. think code run First of all, we want to run the code.
22. run • We don't know whether a code really works well without running it. • More than anything, we:programmer want to run a code just after we wrote it.
23. if __FILE__ == $0 require 'pp' myobj = MyClass.new(:arg) p myobj.do_something pp myobj end Imagine: Run code without test.
24. % irb -r ./my_class > my_obj = MyClass.new > myobj.do_something > myobj OK, we have nice REPL
25. if __FILE__ == $0 require 'pp' alice = Person.create(name: 'alice', age: 24) alisia = Person.create(name: 'alisia', age: 30) bob = Person.create(name: 'bob', age: 18) chris = Person.create(name: 'chris', age: 42) pp Person.name_like('ali') pp Person.younger_than(24) end get more^2 complex
26. $ rails console > alice = Person.create(name: 'alice') > alissa = Person.create(name: 'alissa') > bob = Person.create(name: 'bob') > chris = Person.create(name: 'chris') > > Person.name_like('ali') > Person.younger_than(24) We have nice REPL on Rails, too.
27. if __FILE__ == $0 require 'pp' alice = Person.create(name: 'alice', age: 24) alisia = Person.create(name: 'alisia', age: 30) bob = Person.create(name: 'bob', age: 18) chris = Person.create(name: 'chris', age: 42) pp Person.name_like('ali') pp Person.younger_than(24) end Data setup & teardown Junk data remains, must cleanup by hand.
28. if __FILE__ == $0 require 'pp' alice = Person.create(name: 'alice', age: 24) alisia = Person.create(name: 'alisia', age: 30) bob = Person.create(name: 'bob', age: 18) chris = Person.create(name: 'chris', age: 42) pp Person.name_like('ali') pp Person.younger_than(24) end Assert by your eye Watch output on each run.
29. if __FILE__ == $0 require 'pp' alice = Person.create(name: 'alice', age: 24) alisia = Person.create(name: 'alisia', age: 30) bob = Person.create(name: 'bob', age: 18) chris = Person.create(name: 'chris', age: 42) pp Person.name_like('ali') pp Person.younger_than(24) end Assertions depends on each other Must be careful to maintain data.
30. if __FILE__ == $0 require 'pp' alice = Person.create(name: 'alice', age: 24) alisia = Person.create(name: 'alisia', age: 30) bob = Person.create(name: 'bob', age: 18) chris = Person.create(name: 'chris', age: 42) pp Person.name_like('ali') pp Person.younger_than(24) end Assertions depends on each other It's more painful to maintain DESTRUCTIVE method's. only 1 record needed for `name_like` execution ̇ OMG: change also younger_than result
31. Imagine: Run code without test. • data setup & teardown. • assert by your eye. • Assertions depends on each other They become worse and worse along the software grows up.
32. A testing framework helps to •Arrange a context •Act independently •Assert result automatically
33. describe Person do context '4 people with below' do let!(:alice) { Person.create(name: 'alice', age: 24) } let!(:alissa){ Person.create(name: 'alissa', age: 30) } let!(:bob) { Person.create(name: 'bob', age: 18) } let!(:chris) { Person.create(name: 'chris', age: 42) } describe '.name_like' do subject { Person.name_like('ali').map(&:name) } it { should =~ %w[alice alissa] } end describe '.younger_than' do subject { Person.younger_than(24).map(&:name) } it { should =~ %w[bob] } end end end Run code with test.
34. describe Person do context '4 people with below' do let!(:alice) { Person.create(name: 'alice', age: 24) } let!(:alissa){ Person.create(name: 'alissa', age: 30) } let!(:bob) { Person.create(name: 'bob', age: 18) } let!(:chris) { Person.create(name: 'chris', age: 42) } describe '.name_like' do subject { Person.name_like('ali').map(&:name) } it { should =~ %w[alice alissa] } end describe '.younger_than' do subject { Person.younger_than(24).map(&:name) } it { should =~ %w[bob] } end end end Arrange Run code with test. data setup & teardown.
35. describe Person do context '4 people with below' do let!(:alice) { Person.create(name: 'alice', age: 24) } let!(:alissa){ Person.create(name: 'alissa', age: 30) } let!(:bob) { Person.create(name: 'bob', age: 18) } let!(:chris) { Person.create(name: 'chris', age: 42) } describe '.name_like' do subject { Person.name_like('ali').map(&:name) } it { should =~ %w[alice alissa] } end describe '.younger_than' do subject { Person.younger_than(24).map(&:name) } it { should =~ %w[bob] } end end end Act Run code with test. Act independently.
36. describe Person do context '4 people with below' do let!(:alice) { Person.create(name: 'alice', age: 24) } let!(:alissa){ Person.create(name: 'alissa', age: 30) } let!(:bob) { Person.create(name: 'bob', age: 18) } let!(:chris) { Person.create(name: 'chris', age: 42) } describe '.name_like' do subject { Person.name_like('ali').map(&:name) } it { should =~ %w[alice alissa] } end describe '.younger_than' do subject { Person.younger_than(24).map(&:name) } it { should =~ %w[bob] } end end end Assert Run code with test. Assert result and report obviously.
37. Test drives development by: Structuring execution •Testing framework structure your code execution. •Arrange a context •Act / perform inependentry •Assert result
38. a slightly more complex example http://flic.kr/p/5xKFpY
39. An ordinary search query form with ordinary tables.
40. •An ordinary search query form. •name like •younger than •interest in at least one hobby Person - name (str) - age (int) Hobby - name (str) Interest - person_id(fk) - hobby_id(fk) 1 * * 1
41. think code run What do you do first if you work with more complex issue? Programming workflow
42. think code run Obviously, you think. Test support it. Programming workflow
43. Imagine: You're thinking about.. • Is there any good API or gem...? • What are the preconditions and results? • At the end of all, What API I want to call from other code?
44. • Ok, at first define ActiveRecord's scopes for build name and age condition. • Just use previous example :-). think: Start from easy way
45. describe Person do context '4 people with below' do let!(:alice) { Person.create(name: 'alice', age: 24) } let!(:alissa){ Person.create(name: 'alissa', age: 30) } let!(:bob) { Person.create(name: 'bob', age: 18) } let!(:chris) { Person.create(name: 'chris', age: 42) } describe '.name_like' do subject { Person.name_like('ali').map(&:name) } it { should =~ %w[alice alissa] } end describe '.younger_than' do subject { Person.younger_than(24).map(&:name) } it { should =~ %w[bob] } end end end
46. class Person < ActiveRecord::Base scope :name_like, ->(name) { where("#{table_name}.name LIKE ?", "#{name}%") } scope :younger_than, ->(age) { where("#{table_name}.age < ?", age.to_i) } end
47. • Umm, name of the scope is ... `has_at_least_one_hobby'. • The scope takes an Array of hobbies like ` %w[programming BBQ travel]`. • Ok, I write these to spec. think: How about hobby?
48. describe Person do context '4 people with below' do # snip describe '.has_at_least_one_hobby(hobbies)' do let(:hobbies) { %w[programming BBQ travel] } subject(:people) do Person.has_at_least_one_hobby(hobbies) end end end end Not good name, especially too long.
49. • We extracted person-hobby relation as "interest". • Ruby has `#any?` method to check at least one element matches condition in collection. • Then what if Person.interest_in_any(hobbies) think: Is there better name?
50. describe Person do context '4 people with below' do # snip describe '.interest_in_any(hobbies)' do let(:hobbies) { %w[programming BBQ travel] } subject(:people) do Person.interest_in_any(hobbies) end end end end Looks good.
51. • At least two people required to assert behavior. • One matches the condition and another doesn't • Above may be written in before {}(RSpec) or setup() (Test::Unit) think: Arrange precondition.
52. describe '.interest_in_any(hobbies)' do let(:hobbies) { %w[programming BBQ travel] } before do hobbies.each do |hobby_name| Hobby.create!(name: hobby_name) end Hobby.create!(name: 'baseball') alice.hobbies << Hobby.where(name: 'travel').first bob.hobbies << Hobby.where(name: 'programming').first chris.hobbies << Hobby.where(name: 'baseball').first end subject(:people) { Person.interest_in_any(hobbies) } end
53. • Hmm, then result should be ... think: Assert result
54. describe '.interest_in_any(hobbies)' do let(:hobbies) { %w[programming BBQ travel] } before do hobbies.each do |hobby_name| Hobby.create!(name: hobby_name) end Hobby.create!(name: 'baseball') alice.hobbies << Hobby.where(name: 'travel').first bob.hobbies << Hobby.where(name: 'programming').first chris.hobbies << Hobby.where(name: 'baseball').first end subject(:people) { Person.interest_in_any(hobbies) } it { should =~ [alice, bob] } end
55. http://flic.kr/p/4rxk3X You got a first GOAL
56. describe '.interest_in_any(hobbies)' do let(:hobbies) { %w[programming BBQ travel] } before do hobbies.each do |hobby_name| Hobby.create!(name: hobby_name) end Hobby.create!(name: 'baseball') alice.hobbies << Hobby.where(name: 'travel').first bob.hobbies << Hobby.where(name: 'programming').first chris.hobbies << Hobby.where(name: 'baseball').first end subject(:people) { Person.interest_in_any(hobbies) } it { should =~ [alice, bob] } end If the test passes, you've DONE plain-normal case.
58. • Handle multiple condition posted from a Search form. • in Rails's controller, parameter is parsed into Hash with string value. • and I love form_for • Implement as ActiveModel form object. think: complex query
59. require 'spec_helper' describe PeopleQuery do include_context \ '4 people: alice(24), aliass(30), bob(18), chris(42)' describe '.new(name_like: "ali", younger_than: 25)' do let(:query) { PeopleQuery.new(name_like: 'ali', younger_than: 25) } subject { query.people } it { should == [alice] } end end
60. require 'spec_helper' describe PeopleQuery do include_context \ '4 people: alice(24), aliass(30), bob(18), chris(42)' describe '.new(name_like: "ali", younger_than: 25)' do let(:query) { PeopleQuery.new(name_like: 'ali', younger_than: 25) } subject { query.people } it { should == [alice] } end end Act • PeopleQuery takes multiple condition by Hash • PeopleQuery#people returns conditioned ActiveRecord::Relation think: PeopleQuery API
61. require 'spec_helper' describe PeopleQuery do include_context \ '4 people: alice(24), aliass(30), bob(18), chris(42)' describe '.new(name_like: "ali", younger_than: 25)' do let(:query) { PeopleQuery.new(name_like: 'ali', younger_than: 25) } subject { query.people } it { should == [alice] } end end Arrange
62. require 'spec_helper' describe PeopleQuery do include_context \ '4 people: alice(24), aliass(30), bob(18), chris(42)' describe '.new(name_like: "ali", younger_than: 25)' do let(:query) { PeopleQuery.new(name_like: 'ali', younger_than: 25) } subject { query.people } it { should == [alice] } end end Assert You've also got a goal for the step.
63. http://flic.kr/p/4rxk3X You got a 2nd GOAL
64. require 'spec_helper' describe PeopleQuery do include_context \ '4 people: alice(24), aliass(30), bob(18), chris(42)' describe '.new(name_like: "ali", younger_than: 25)' do let(:query) { PeopleQuery.new(name_like: 'ali', younger_than: 25) } subject { query.people } it { should == [alice] } end end FAQ: How much should I do test? You may test until you get a goal.
65. • Think: good wrapper for Person.interest_any?() • How the API used, maybe from controller, then user input will be parsed into Hash with string value... think: How about hobby
66. describe '.new(name_like: "ali", hobbies: "baseball")' do include_context \ 'there are 4 hobbies: programming, travel, BBQ and baseball' let(:query) { PeopleQuery.new(name_like: 'ali', hobbies: 'baseball travel') } before do alice.hobbies << Hobby.where(name: 'BBQ') alissa.hobbies << Hobby.where(name: 'baseball') end subject { query.people } it { should == [alissa] } end 3 condition handling with simple case is DONE.
67. class PeopleController < ApplicationController def index @query = PeopleQuery.new(params[:q]) @people = @query.people end end = form_for @query, url: :people, as: 'q', method: :get do |f| = f.search_field :name_like = f.number_field :younger_than = f.search_field :hobbies = f.actions do = f.submit 'Search' %ul.people-found - @people.each do |person| %li[person, :found]= person.name
68. Steps for test to drive development • Think how your object act, method name, arguments and return val. • Arrange testing context. There are many advanced technique. • Write simple assertion case.
69. Test drives development by: being try & error canvas. • Write code, read it and think how call it. • Share with and think together with collaborators agains real code. • Run it and get feedback.
70. think code run TDD supports both think and code. Programming workflow
71. TDD has many other approach • Many technics • Fake it & Triangulation. • Data generation: fixture replacement • Test doubles • Assert first approach is also welcome. • Better for too difficult not to come up with solution. • But MOST IMPORTANT thing is...
72. http://flic.kr/p/zBdU7 Test Drives Development • run: by structuring execution. • think: by being try and error canvas. • Also be useful in future: support refactoring and report regression.
73. think code run Programming workflow
74. think code run The more difficult a code you write, the helpful this approach can be. Programming workflow
76. Thank you for listening. - May it be a light for you in dark places, when all other lights go out. - May it be a light for you in dark places, when all other lights go out.
77. Questions?
78. FAQ. How about cuke, T/U, shoulda or ... ? • It's not matter. • code > run > think loop should be test framework agnostic .