Test-Driven Development with Python

A TDD tutorial, featuring unittest, LiveServerTestCase, and Selenium. Originally presented at PyTennessee 2016.

Transcript

1. Test-Driven Development with Python 7 February 2016 Kevin Harvey @kevinharvey kcharvey@gmail.com
2. Who is this guy? Senior Python Developer at axialHealthcare Djangonaut since 2007 (version 0.96)
10. What is a test? An evolutionary perspective
11. 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
12. 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
13. What is a test? An evolutionary perspective >>> from myapp.my_funcs import multiply_these_two_numbers >>> multiply_these_two_numbers(4,5) 20
14. 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)
15. What is a test? An evolutionary perspective # my_tests.py from myapp.my_funcs import multiply_these_two_numbers print multiply_these_two_numbers(4,5) $ python my_tests.py 20 $
16. What is a test? An evolutionary perspective >>> import time >>> time.sleep(604800)
18. What is a test? An evolutionary perspective $ python my_tests.py 20 $
19. What is a test? An evolutionary perspective from unittest 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)
20. 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'...
21. Why write tests? Why are we doing this?
22. Why write tests? 1. Drink More Beer
23. Why write tests? 2. Take the fear out of refactoring
24. 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
25. 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)
26. Why write tests? UGLY, VITAL, TESTED CODE from unittest 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)
27. Why write tests? BETTER 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 return a*b
28. 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'...
29. Why write tests? 3. Explain your code
30. Why write tests? 4. Clarify your thinking
31. Why write tests? 5. Allow more developers to contribute
32. Why write tests? 6. Be taken seriously
33. Types of Tests 1. Functional tests 2. Unit tests 3. Performance tests (which I won’t cover)
34. Types of Tests 1. Functional tests 2. Unit tests 3. Performance tests (which I won’t cover)
35. What’s the Difference? Fewer things (ideally one) Many things (possibly all) Unit Functional
36. What’s the Difference? Small, write many Big, write few Unit Functional
37. What’s the Difference? Stuff developers care about Stuff users care about Unit Functional
38. What’s the Difference? Fast Slow Unit Functional
39. A few examples Python tests in action!
40. Unit test for Django 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
41. Unit test for Django 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
42. Arrange, Act, Assert 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) The Three A’s
43. Arrange, Act, Assert 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) The Three A’s
44. Arrange, Act, Assert 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) The Three A’s
45. Arrange, Act, Assert 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) The Three A’s
46. 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
47. Unit test for a Form class QuestionForm(forms.ModelForm): class Meta: model = Question fields = ('text',) A few examples
48. 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
49. 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'), ...
50. 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
51. Functional test: Logging in # set up the admin site A few examples
52. Test-Driven Development What is Test-Driven Development?
53. Test-Driven Development Step One: Figure out your user experience.
54. Invoking a command line utility # test.py import unittest import subprocess class StardateTestCase(unittest.TestCase): def test_stardate(self): """ Test that we return the current stardate """ output = subprocess.check_output('stardate', shell=True) self.assertEqual(output, '93705.51') if __name__ == '__main__': unittest.main() TDD a CLI
55. Invoking a command line utility $ python test.py /bin/sh: stardate: command not found E ================================================================= ERROR: test_stardate (__main__.StardateTestCase) Test that we return the current stardate ----------------------------------------------------------------- Traceback (most recent call last): File "test.py", line 11, in test_stardate output = subprocess.check_output("stardate", shell=True) File "/usr/local/Cellar/python/2.7.10_2/Frameworks/ Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 573, in check_output raise CalledProcessError(retcode, cmd, output=output) CalledProcessError: Command 'stardate' returned non-zero exit status 127 ----------------------------------------------------------------- TDD a CLI
56. TDD by Example Our example project: Torquemada
57. TDD by Example http://bit.ly/1jmHfjp or http://floating-inlet-6675.herokuapp.com/ code: https://github.com/kevinharvey/Test-driven-Django- Development or use the link at the demo
58. TDD by Example Torquemada allows attendees at “Test-Driven Development with Python” to inquire of the presenter asynchronously. Our example project: Torquemada http://bit.ly/1jmHfjp
59. Let’s do this. TDD by example
60. Let’s do this Let’s do this.
63. Text
64. 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() ...
65. 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')
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68. 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")
69. Text
70. We have a working (but failing) test. TDD by example
71. So, where are we exactly? TDD by example
76. 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
82. Rinse and repeat. TDD by example
83. Getting Around with Selenium self.browser.get()
84. Getting Around with Selenium self.browser.find_element_by_<METHOD>()
85. 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
86. 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
87. Getting Around with Selenium element.click()
88. 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
89. How do I get started? I want to start testing on my team. What’s the best way?
90. How do I get started? 1. Write tests for bug reports
91. How do I get started? 2. Use TDD for new features
92. How do I get started? 3. Write unit tests for existing code you use while doing 1. and 2.
93. Next Steps Continuous Integration https://github.com/kmmbvnr/django-jenkins Jenkins
94. Thanks! @kevinharvey https://speakerdeck.com/kevinharvey/ test-driven-django-development axialHealthcare is hiring! DM me.
95. What about continuous integration?
96. What about continuous integration? I like Jenkins.
97. .WAR
98. WHAT
99. IS
100. IT
101. GOOD
102. FOR?
103. What about continuous integration? But in this case I’ll make an exception.
104. 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
105. Configuring Jenkins $ wget http://mirrors.jenkins-ci.org/war/latest/jenkins.war $ java -jar jenkins.war http://localhost:8080
106. Configuring Jenkins You’ll need some plugins: - Jenkins Violations Plugin - Jenkins Git Plugin - Jenkins Cobertura Plugin
107. 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”
108. Configuring Jenkins DONE