Test-Driven Django Development

Writing tests is not just about knowing whether your code is broken. TDD is a development methodology that simplifies software projects, helping you think through your app before you even write the first model. We'll cover what to test and how to test it, and walk through some of Django's testing tools in tons of examples and a TDD demo.

This presentation was given at PyTennessee on February 8, 2015.

Transcript

1. Test-Driven Django Development ! 8 February 2015 Kevin Harvey @kevinharvey kcharvey@gmail.com
2. Who is this guy? Senior Systems Engineer at SmileCareClub Djangonaut since 2007 (version 0.96)
4. Who are y’all? A quick poll...
5. What is a test? An evolutionary perspective
6. What is a test? An evolutionary perspective def multiply_these_two_numbers(a,b): """ Add 'b' to itself 'a' times """ i = 0 product = 0 while a > i: product += b i += 1 return product
7. What is a test? An evolutionary perspective >>> from myapp.my_funcs import multiply_these_two_numbers >>> multiply_these_two_numbers(4,5) 20 >>> multiply_these_two_numbers(7,8) 56 >>> multiply_these_two_numbers(720,617) 444240
8. What is a test? An evolutionary perspective >>> from myapp.my_funcs import multiply_these_two_numbers >>> multiply_these_two_numbers(4,5) 20
9. What is a test? An evolutionary perspective from myapp.my_funcs import multiply_these_two_numbers import math ! def area_of_rectangle(length, width): """ Length times width """ return multiply_these_two_numbers(length, width) def surface_area_of_sphere(radius): """ 4 times pi times the radius squared """ radius_squared = multiply_these_two_numbers(radius, radius) four_times_pi = multiply_these_two_numbers(4, math.pi) return multiply_these_two_numbers(radius_squared, four_times_pi)
10. What is a test? An evolutionary perspective from myapp.my_funcs import multiply_these_two_numbers ! print multiply_these_two_numbers(4,5) $ python my_tests.py 20 $
11. What is a test? An evolutionary perspective >>> import time >>> time.sleep(604800)
13. What is a test? An evolutionary perspective $ python my_tests.py 20 $
14. What is a test? An evolutionary perspective from django.test import TestCase from myapp.my_funcs import multiply_these_two_numbers ! class SillyTest(TestCase): def test_multiply_these_two_numbers(self): """ Tests that the function knows how to do math """ self.assertEqual(multiply_these_two_numbers(4,5), 20)
15. What is a test? An evolutionary perspective $ python manage.py test myapp Creating test database for alias 'default'... . --------------------------------------------------------- Ran 1 test in 0.000s ! OK Destroying test database for alias 'default'...
16. Why write tests? Why are we doing this?
17. Why write tests? 1. Drink More Beer
18. Why write tests? 2. Take the fear out of refactoring
19. Why write tests? UGLY CODE def multiply_these_two_numbers(a,b): """ Add 'b' to itself 'a' times """ i = 0 product = 0 while a > i: product += b i += 1 return product
20. Why write tests? UGLY, VITAL CODE from myapp.my_funcs import multiply_these_two_numbers import math ! def area_of_rectangle(length, width): """ Length times width """ return multiply_these_two_numbers(length, width) def surface_area_of_sphere(radius): """ 4 times pi times the radius squared """ radius_squared = multiply_these_two_numbers(radius, radius) four_times_pi = multiply_these_two_numbers(4, math.pi) return multiply_these_two_numbers(radius_squared, four_times_pi)
21. Why write tests? UGLY, VITAL, TESTED CODE from django.test import TestCase from myapp.my_funcs import multiply_these_two_numbers ! class SillyTest(TestCase): def test_multiply_these_two_numbers(self): """ Tests that the function knows how to do math """ self.assertEqual(multiply_these_two_numbers(4,5), 20)
22. Why write tests? BETTER CODE def multiply_these_two_numbers(a,b): """ Multiply a times b """ # i = 0 # product = 0 # while a > i: # product += b # i += 1 # return product return a*b
23. Why write tests? The test guarantees the refactor $ python manage.py test myapp Creating test database for alias 'default'... . --------------------------------------------------------- Ran 1 test in 0.000s ! OK Destroying test database for alias 'default'...
24. Why write tests? 3. Explain your code
25. Why write tests? 4. Clarify your thinking
26. Why write tests? 5. Allow more developers to contribute
27. Why write tests? 6. Be taken seriously
28. Why write tests? 7. Try something out before you screw up your dev environment
29. Why write tests? Keep your dev database clean $ python manage.py test myapp Creating test database for alias 'default'... . --------------------------------------------------------- Ran 1 test in 0.000s ! OK Destroying test database for alias 'default'...
30. Types of Tests 1.Functional tests 2.Unit tests 3.Performance tests (which I won’t cover)
31. What’s the Difference? Fewer things (ideally one) Many things (possibly all) Unit Functional
32. What’s the Difference? Small, write many Big, write few Unit Functional
33. What’s the Difference? Stuff developers care about Stuff users care about Unit Functional
34. What’s the Difference? Fast Slow Unit Functional
35. A few examples Django tests in action!
36. Unit test for Model def test_questions_increment_votes_up(self): """ Test voting up a question """ question_1 = Question(text="How can my team get started?", votes=7) question_1.increment_votes(4) self.assertEquals(question_1.votes, 11) A few examples
37. Unit test for Model class Question(models.Model): text = models.CharField("Question", max_length=500) votes = models.IntegerField() def increment_votes(self, num): self.votes += num self.save() A few examples
38. Unit test for a Form def test_question_form_excludes_all_but_text(self): """ The user can only supply the text of a question """ form = QuestionForm() self.assertEquals(form.fields.keys(), ['text']) self.assertNotEquals(form.fields.keys(), ['text', 'votes']) A few examples
39. Unit test for a Form class QuestionForm(forms.ModelForm): class Meta: model = Question fields = ('text',) A few examples
40. Unit test for a POST action def test_ask_question(self): """ Test that POSTing the right data will result in a new question """ response = self.client.post('/ask/', {'text': 'Is there any more pizza?'}) self.assertRedirects(response, '/') self.assertEqual(Question.objects.filter(text='Is there any more pizza?').count(), 1) A few examples
41. Unit test for a POST action def ask(request): if request.method == "POST": question_form = QuestionForm(request.POST) question_form.save() return HttpResponseRedirect('/') A few examples urlpatterns = patterns('', ... ! url(r'^ask/$', 'questions.views.ask', name='ask'), ...
42. Functional test: Logging in def test_admin_can_manage_questions(self): ! self.browser.get(self.live_server_url + '/admin/') username = self.browser.find_element_by_css_selector("input#id_username") username.send_keys("peter") password = self.browser.find_element_by_css_selector("input#id_password") password.send_keys("password") self.browser.find_element_by_css_selector("input[type='submit']").click() ! body = self.browser.find_element_by_tag_name('body') self.assertIn('Site administration', body.text) A few examples
43. Functional test: Logging in # set up the admin site A few examples
44. Test Driven Development What is Test Driven Development?
45. TDD by Example Our example project: Torquemada
46. TDD by Example http://bit.ly/1jmHfjp or http://floating-inlet-6675.herokuapp.com/ ! code: https://github.com/kcharvey/Test-driven-Django- Development or use the link at the demo
47. TDD by Example Torquemada allows attendees at “Test-Driven Django Development” to inquire of the presenter asynchronously. Our example project: Torquemada http://bit.ly/1jmHfjp
48. TDD by Example Use Case: Isabella the Inquisitive Isabella has learned a lot by attending the “Test-driven Django Development” at PyTennessee but still has a few questions for the presenter. She visits Torquemada in her web browser, where she can see if any of her inquiries have been addressed and see the question that is being currently discussed. She is able to ‘vote up’ questions she would like the presenter to answer, and ‘vote down’ questions she thinks are unimportant. She is also able to ask her own question. Our example project: Torquemada http://bit.ly/1jmHfjp
49. TDD by Example Use Case: Peter the Presenter Peter is presenting“Test-driven Django Development” at PyTennessee and would like to answer any questions the attendees may have during set periods in the talk. He views Torquemada in his web browser to see what questions attendees have asked, and their relative importance based on the number of votes they’ve received. When the group is discussing a question, he uses the Django admin site to set the question’s status to “Current”. After the question has been discussed, he sets the status to “Archived” Our example project: Torquemada http://bit.ly/1jmHfjp
50. Let’s do this. TDD by example
51. Let’s do this Let’s do this.
54. Text
55. TDD by example Text from django.test import LiveServerTestCase from selenium import webdriver ! class QuestionsTest(LiveServerTestCase): ! def setUp(self): self.browser = webdriver.Firefox() self.browser.implicitly_wait(3) ! def tearDown(self): self.browser.quit() ...
56. TDD by example Text ... class QuestionsTest(LiveServerTestCase): ... def test_can_read_v..._a_question(self): # Isabel opens her web browser and # visits Torquemada self.browser.get(self.live_server_url + '/') ! # TODO self.fail('finish this test')
57. Text
58. Text
59. TDD by example Text # She knows it's Torquemada because she sees the name in the heading heading = self.browser.find_element_by_css_selector("h1#trq-heading") self.assertEqual(heading.text, "Torquemada")
60. Text
61. We have a working (but failing) test. Commit it. TDD by example
62. So, where are we exactly? TDD by example
67. TDD by example # run all the tests in our entire project python manage.py test ! # run all the tests for an app python manage.py test questions ! # run all the tests in a test case python manage.py test questions.HomePageViewTest ! # run a single test python manage.py test questions.HomePageViewTest.test_root_url_shows_questions
73. Rinse and repeat. TDD by example
74. Getting Around with Selenium self.browser.get()
75. Getting Around with Selenium self.browser.find_element_by_<METHOD>()
76. Getting Around with Selenium find_element_by_id find_element_by_name find_element_by_xpath find_element_by_link_text find_element_by_partial_link_text find_element_by_tag_name find_element_by_class_name find_element_by_css_selector # use this one
77. Getting Around with Selenium find_elements_by_id find_elements_by_name find_elements_by_xpath find_elements_by_link_text find_elements_by_partial_link_text find_elements_by_tag_name find_elements_by_class_name find_elements_by_css_selector ! # return lists
78. Getting Around with Selenium element.click()
79. Getting Around with Selenium text_field = self.browser.find_element_by_css_selector("#id_text") text_field.clear() text_field.send_keys("Why aren't you using reverse()?") ! self.browser.find_element_by_css_selector("input#trq-submit- question").click() Working with form elements
80. How do I get started? I want to start testing on my team. What’s the best way?
81. How do I get started? 1. Write tests for bug reports
82. How do I get started? 2. Use TDD for new features
83. How do I get started? 3. Write unit tests for existing code you use while doing 1. and 2.
84. Next Steps Continuous Integration https://github.com/kmmbvnr/django-jenkins Jenkins
85. Thanks! @kevinharvey ! http://www.smilecareclub.com/ ! SmileCareClub is hiring! DM me.
86. Resources • https://github.com/kmmbvnr/django- jenkins • https://sites.google.com/site/kmmbvnr/ home/django-jenkins-tutorial • http://jenkins-ci.org/ Jenkins
87. Resources • http://funkload.nuxeo.org/ • http://jmeter.apache.org/ • http://httpd.apache.org/docs/2.2/ programs/ab.html Performance Testing
88. What about continuous integration?
89. What about continuous integration? I like Jenkins.
90. .WAR
91. WHAT
92. IS
93. IT
94. GOOD
95. FOR?
96. What about continuous integration? But in this case I’ll make an exception.
97. Configuring Jenkins $ pip install django-jenkins INSTALLED_APPS = ( ... 'django_jenkins', ) ... ! JENKINS_TASKS = ( 'django_jenkins.tasks.run_pylint', 'django_jenkins.tasks.with_coverage', 'django_jenkins.tasks.django_tests', # there are more of these ) ! $ python manage.py jenkins # Jenkins will run this command
98. Configuring Jenkins $ wget http://mirrors.jenkins-ci.org/war/latest/jenkins.war $ java -jar jenkins.war ! http://localhost:8080
99. Configuring Jenkins You’ll need some plugins: - Jenkins Violations Plugin - Jenkins Git Plugin - Jenkins Cobertura Plugin
100. Configuring Jenkins 1. Configure a new test (name, description) 2. Give it your repo URL 3. Tell it how often to build 4. Tell it the commands to run 5. Configure where to save the reports 6. Click “Build Now”
101. Configuring Jenkins DONE
102. Using fixtures Manage data for tests runs
103. Using fixtures [ { "pk": 1, "model": "questions.question", "fields": { "status": "new", "text": "How can my team get started with testing?", "votes": 0, "created": "2013-01-17T16:15:37.786Z" } }, { "pk": 2, "model": "questions.question", "fields": { "status": "new", "text": "Does Selenium only work in Firefox?", "votes": 0, "created": "2013-01-17T16:17:48.381Z" } } ]
104. Using fixtures $ python manage.py runserver ... ! # Use the Django /admin site to make some test data ! ... ! $ mkdir questions/fixtures/ $ python manage.py dumpdata questions --indent=4 > questions/fixtures/questions.json Do NOT try to write fixtures by hand