Test-Driven Development with Python

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Test-Driven Development with Python 7 February 2016 Kevin Harvey @kevinharvey [email protected]

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Who is this guy? Senior Python Developer at axialHealthcare Djangonaut since 2007 (version 0.96)

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What is a test? An evolutionary perspective

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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

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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

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What is a test? An evolutionary perspective >>> from myapp.my_funcs import multiply_these_two_numbers >>> multiply_these_two_numbers(4,5) 20

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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)

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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 $

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What is a test? An evolutionary perspective >>> import time >>> time.sleep(604800)

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What is a test? An evolutionary perspective $ python my_tests.py 20 $

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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)

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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'...

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Why write tests? Why are we doing this?

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Why write tests? 1. Drink More Beer

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Why write tests? 2. Take the fear out of refactoring

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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

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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)

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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)

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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

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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'...

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Why write tests? 3. Explain your code

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Why write tests? 4. Clarify your thinking

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Why write tests? 5. Allow more developers to contribute

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Why write tests? 6. Be taken seriously

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Types of Tests 1. Functional tests 2. Unit tests 3. Performance tests (which I won’t cover)

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Types of Tests 1. Functional tests 2. Unit tests 3. Performance tests (which I won’t cover)

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What’s the Difference? Fewer things (ideally one) Many things (possibly all) Unit Functional

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What’s the Difference? Small, write many Big, write few Unit Functional

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What’s the Difference? Stuff developers care about Stuff users care about Unit Functional

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What’s the Difference? Fast Slow Unit Functional

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A few examples Python tests in action!

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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

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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

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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

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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

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Unit test for a Form class QuestionForm(forms.ModelForm): class Meta: model = Question fields = ('text',) A few examples

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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

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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'), ...

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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

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Functional test: Logging in # set up the admin site A few examples

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Test-Driven Development What is Test-Driven Development?

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Test-Driven Development Step One: Figure out your user experience.

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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

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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

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TDD by Example Our example project: Torquemada

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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

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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

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Let’s do this. TDD by example

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Let’s do this Let’s do this.

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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() ...

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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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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")

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We have a working (but failing) test. TDD by example

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So, where are we exactly? TDD by example

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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

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Rinse and repeat. TDD by example

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Getting Around with Selenium self.browser.get()

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Getting Around with Selenium self.browser.ﬁnd_element_by_()

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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

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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

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Getting Around with Selenium element.click()

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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

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How do I get started? I want to start testing on my team. What’s the best way?

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How do I get started? 1. Write tests for bug reports

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How do I get started? 2. Use TDD for new features

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How do I get started? 3. Write unit tests for existing code you use while doing 1. and 2.

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Next Steps Continuous Integration https://github.com/kmmbvnr/django-jenkins Jenkins

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Thanks! @kevinharvey https://speakerdeck.com/kevinharvey/ test-driven-django-development axialHealthcare is hiring! DM me.

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What about continuous integration?

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What about continuous integration? I like Jenkins.

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.WAR

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WHAT

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GOOD

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FOR?

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What about continuous integration? But in this case I’ll make an exception.

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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

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Conﬁguring Jenkins $ wget http://mirrors.jenkins-ci.org/war/latest/jenkins.war $ java -jar jenkins.war http://localhost:8080

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Conﬁguring Jenkins You’ll need some plugins: - Jenkins Violations Plugin - Jenkins Git Plugin - Jenkins Cobertura Plugin

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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”

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Conﬁguring Jenkins DONE