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TESTING in DJANGO by Ana Balica

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@anabalica

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Questions?

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Django archeology 1.0

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Django archeology 1.0 1.11 1.1 1.10 …

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#2333 Add unit test framework for end-user Django applications

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#2333 As an added incentive, this is a feature that is present in Rails. Add unit test framework for end-user Django applications ”

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./manage.py test 1.0

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./manage.py test app.TestClass.test_method 1.0

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TEST RUNNER 1.0 setup test environment tests.py models.py teardown & results

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Client 1.0 get post login logout

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testcase 1.0 1.0 assert* Redirects (Not)Contains FormError Template(Not)Used

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1.1

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Client 1.1 put head delete options

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TestCase 1.1 TransactionTestCase

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1.1 my test enter transaction rollback transaction I am a TestCase burger

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1.1 I am a TransactionTestCase. I flush the database before each test.

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1.2

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DjangoTestSuiteRunner from function to class

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1.2 failures = test_runner(test_labels, verbosity, interactive) if failures: sys.exit(failures)

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1.2 failures = test_runner(test_labels, verbosity, interactive) if failures: sys.exit(failures)

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1.2 0 success failures = test_runner(test_labels, verbosity, interactive) if failures: sys.exit(failures)

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1.2 1 failure failures = test_runner(test_labels, verbosity, interactive) if failures: sys.exit(failures)

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1.2 42 failure failures = test_runner(test_labels, verbosity, interactive) if failures: sys.exit(failures)

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1.2 256 success failures = test_runner(test_labels, verbosity, interactive) if failures: sys.exit(failures)

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1.2 failures = TestRunner(verbosity, interactive, failfast) if failures: sys.exit(1)

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1.2 failures = TestRunner(verbosity, interactive, failfast) if failures: sys.exit(1)

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1.2 0 / 1 success failure

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failures = TestRunner(verbosity, interactive, failfast) if failures: sys.exit(1) 1.2 256 failure

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failures = TestRunner(verbosity, interactive, failfast) if failures: sys.exit(1) 1.2 256 failure

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failures = TestRunner(verbosity, interactive, failfast) if failures: sys.exit(1) 1.2 256 failure

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failures = TestRunner(verbosity, interactive, failfast) if failures: sys.exit(1) 1.2 256 failure

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failures = TestRunner(verbosity, interactive, failfast) if failures: sys.exit(1) 1.2 256 failure

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1.2 multiple databases

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1.2 multiple databases

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1.2 multiple databases primary replica

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1.2 multiple databases DATABASES = { 'default': { 'HOST': 'dbprimary', # ... plus other settings }, 'replica': { 'HOST': 'dbreplica', 'TEST_MIRROR': 'default', # ... plus other settings } }

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1.2 multiple databases DATABASES = { 'default': { 'HOST': 'dbprimary', # ... plus other settings }, 'replica': { 'HOST': 'dbreplica', 'TEST_MIRROR': 'default', # ... plus other settings } }

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multiple databases DATABASES = { 'default': { 'HOST': 'dbprimary', # ... plus other settings }, 'replica': { 'HOST': 'dbreplica', 'TEST': { 'MIRROR': 'default', }, # ... plus other settings } }

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multiple databases DATABASES = { 'default': { 'HOST': 'dbprimary', # ... plus other settings }, 'replica': { 'HOST': 'dbreplica', 'TEST': { 'MIRROR': 'default', }, # ... plus other settings } }

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1.2 multiple databases primary replica

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1.2 multiple databases primary replica

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1.2 multiple databases primary replica

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1.3

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testcase 1.0 1.3 assert* QuerysetEqual NumQueries

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1.3 RequestFactory Client

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1.3 class RequestFactory(object): def request(self, **request): return WSGIRequest(self._base_environ(**request))

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1.3 doctests = tests + documentation

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1.3 doctests = tests + documentation

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1.4

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1.4 Transaction TestCase TestCase

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1.4 Transaction TestCase TestCase Simple TestCase LiveServer TestCase

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1.4 Transaction TestCase TestCase Simple TestCase LiveServer TestCase doesn’t hit the database

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1.4 Transaction TestCase TestCase Simple TestCase LiveServer TestCase doesn’t hit the database runs an http server

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1.4 Transaction TestCase TestCase Simple TestCase LiveServer TestCase doesn’t hit the database runs an http server

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1.5

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1.5 I am a TransactionTestCase. I flush the database before each test.

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1.5 I am a TransactionTestCase. I flush the database before each test. after

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1.5 flush run TransactionTestCase enter transaction run TestCase rollback transaction {

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1.5 flush run TransactionTestCase enter transaction run TestCase rollback transaction { dirty state

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1.5 flush {run TransactionTestCase enter transaction run TestCase rollback transaction

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1.5 flush { run TransactionTestCase enter transaction run TestCase rollback transaction

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1.5 flush {run TransactionTestCase enter transaction run TestCase rollback transaction

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1.5 flush {run TransactionTestCase enter transaction run TestCase rollback transaction

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1.5 flush {run TransactionTestCase enter transaction run TestCase rollback transaction problem solved

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1.6

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Client 1.6 patch

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1.6 TEST_RUNNER improvements Test discovery Full paths vs pseudo paths Doctests discovery

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1.6 TEST_RUNNER improvements Test discovery Full paths vs pseudo paths Doctests discovery

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1.6 TEST_RUNNER improvements Test discovery Full paths vs pseudo paths Doctests discovery

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1.7

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1.7 unittest2

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1.7 unittest2 unittest

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1.7 LiveServerTestCase StaticLiveServerTestCase

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1.8

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Client 1.8 trace

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TestCase before enter atomic load fixtures … exit atomic close connections 1.8

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TestCase before enter atomic load fixtures … exit atomic close connections 1.8

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TestCase before enter atomic load fixtures … exit atomic close connections } times # of tests 1.8

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TestCase after enter atomic load fixtures enter atomic … exit atomic exit atomic close connections 1.8

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TestCase after enter atomic load fixtures enter atomic … exit atomic exit atomic close connections { once 1.8

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TestCase after enter atomic load fixtures enter atomic … exit atomic exit atomic close connections } times # of tests { once 1.8

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1.9

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1.9 --parallel

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1.9

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1.9 workers

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1.9 workers databases

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1.9 workers databases suite

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1.9 workers databases partitions

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1.9 workers databases partitions

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1.9 workers databases partitions

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1.9 workers databases partitions

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1.9 workers databases partitions

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1.9 workers databases partitions

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1.9 workers databases partitions

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nose multiprocess plugin

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1.10

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1.10 class SampleTestCase(TestCase): @tag('slow') def test_slow(self): ...

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1.10 ./manage.py test --tag=slow class SampleTestCase(TestCase): @tag('slow') def test_slow(self): ...

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1.10 ./manage.py test --tag=slow ./manage.py test --exclude-tag=slow class SampleTestCase(TestCase): @tag('slow') def test_slow(self): ...

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nose attrib plugin py.test markers

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nose attrib plugin py.test markers will do the same

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1.11

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# Starting with Python 3.4 def test_even(self): for i in range(0, 6): with self.subTest(i=i): self.assertEqual(i % 2, 0)

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# Starting with Python 3.4 def test_even(self): for i in range(0, 6): with self.subTest(i=i): self.assertEqual(i % 2, 0)

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# Starting with Python 3.4 def test_even(self): for i in range(0, 6): with self.subTest(i=i): self.assertEqual(i % 2, 0) --parallel

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TEST bed or what happens when you run ./manage.py test

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$ ./manage.py test 1

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TestRunner = get_runner(settings, options['testrunner']) test_runner = TestRunner(**options) failures = test_runner.run_tests(test_labels) ../management/commands/test.py 2

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TestRunner = get_runner(settings, options['testrunner']) test_runner = TestRunner(**options) failures = test_runner.run_tests(test_labels) ../management/commands/test.py 2

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3 self.setup_test_environment()

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3 self.setup_test_environment() locmem email backend

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3 self.setup_test_environment() locmem email backend instrumented test renderer

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3 self.setup_test_environment() locmem email backend instrumented test renderer deactivate translations

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4 self.build_suite(test_labels, extra_tests)

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4 self.build_suite(test_labels, extra_tests)

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5 self.setup_databases() 7 self.run_suite(suite) 8 self.teardown_databases(old_config) 6 self.run_checks()

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5 self.setup_databases() 7 self.run_suite(suite) 8 self.teardown_databases(old_config) 6 self.run_checks()

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5 self.setup_databases() 7 self.run_suite(suite) 8 self.teardown_databases(old_config) 6 self.run_checks()

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5 self.setup_databases() 7 self.run_suite(suite) 8 self.teardown_databases(old_config) 6 self.run_checks()

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9 self.teardown_test_environment()

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original email backend 9 self.teardown_test_environment()

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original email backend 9 original test renderer self.teardown_test_environment()

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original email backend 9 original test renderer delete state and mailbox self.teardown_test_environment()

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10 self.suite_result(suite, result) len(result.failures) + len(result.errors) if failures: sys.exit(1)

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test classes

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SimpleTestCase TransactionTestCase TestCase LiveServerTestCase StaticLiveServerTestCase

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SimpleTestCase no database queries access to test client fast

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TransactionTestCase allows database queries access to test client fast allows database transactions flushes database after each test

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TestCase allows database queries access to test client faster restricts database transactions runs each test in a transaction

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LiveServerTestCase acts like TransactionTestCase launches a live HTTP server in a separate thread

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StaticLiveServerTestCase acts like TransactionTestCase launches a live HTTP server in a separate thread serves static files

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Client

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Client RequestFactory ClientHandler

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Client RequestFactory ClientHandler constructs requests encodes data

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Client RequestFactory ClientHandler constructs requests encodes data

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Client RequestFactory ClientHandler constructs requests encodes data

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Client RequestFactory ClientHandler stateful response++ handles redirects constructs requests encodes data

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Client RequestFactory ClientHandler stateful response++ handles redirects constructs requests encodes data

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Client RequestFactory ClientHandler stateful response++ handles redirects constructs requests encodes data

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Client RequestFactory ClientHandler stateful response++ handles redirects constructs requests encodes data

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Client RequestFactory ClientHandler stateful response++ handles redirects loads middleware emulates disables CSRF constructs requests encodes data

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Client RequestFactory ClientHandler stateful response++ handles redirects loads middleware emulates disables CSRF constructs requests encodes data

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Client RequestFactory ClientHandler stateful response++ handles redirects loads middleware emulates disables CSRF constructs requests encodes data

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Client RequestFactory ClientHandler stateful response++ handles redirects loads middleware emulates disables CSRF constructs requests encodes data

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Client RequestFactory ClientHandler stateful response++ handles redirects loads middleware emulates disables CSRF constructs requests encodes data

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Quality

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Factory Boy fixtures replacement with random and realistic values

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Factory Boy fixtures replacement with random and realistic values generated by Faker

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property based testing with Hypothesis

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from hypothesis import given from hypothesis.strategies import text @given(text()) def test_decode_inverts_encode(s): assert decode(encode(s)) == s

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from hypothesis import given from hypothesis.strategies import text @given(text()) def test_decode_inverts_encode(s): assert decode(encode(s)) == s

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from hypothesis import given from hypothesis.strategies import text @given(text()) def test_decode_inverts_encode(s): assert decode(encode(s)) == s

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from hypothesis import given from hypothesis.strategies import text @given(text()) def test_decode_inverts_encode(s): assert decode(encode(s)) == s

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from hypothesis import given from hypothesis.strategies import text @given(text()) def test_decode_inverts_encode(s): assert decode(encode(s)) == s

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from hypothesis import given from hypothesis.strategies import text @given(text()) def test_decode_inverts_encode(s): assert decode(encode(s)) == s rerun for different values

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from hypothesis.extra.django.models import models from hypothesis.strategies import integers models(Customer).example() models(Customer, age=integers( min_value=0, max_value=120) ).example()

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from hypothesis.extra.django.models import models from hypothesis.strategies import integers models(Customer).example() models(Customer, age=integers( min_value=0, max_value=120) ).example()

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from hypothesis.extra.django import TestCase from hypothesis import given from hypothesis.extra.django.models import models from hypothesis.strategies import lists, integers class TestProjectManagement(TestCase): @given( models(Project, collaborator_limit=integers(min_value=0, max_value=20)), lists(models(User), max_size=20)) def test_can_add_users_up_to_collaborator_limit(self, project, collaborators): for c in collaborators: if project.at_collaboration_limit(): with self.assertRaises(LimitReached): project.add_user(c) self.assertFalse(project.team_contains(c)) else: project.add_user(c) self.assertTrue(project.team_contains(c))

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from hypothesis.extra.django import TestCase from hypothesis import given from hypothesis.extra.django.models import models from hypothesis.strategies import lists, integers class TestProjectManagement(TestCase): @given( models(Project, collaborator_limit=integers(min_value=0, max_value=20)), lists(models(User), max_size=20)) def test_can_add_users_up_to_collaborator_limit(self, project, collaborators): for c in collaborators: if project.at_collaboration_limit(): with self.assertRaises(LimitReached): project.add_user(c) self.assertFalse(project.team_contains(c)) else: project.add_user(c) self.assertTrue(project.team_contains(c))

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class TestProjectManagement(TestCase): @given( models(Project, collaborator_limit=integers(min_value=0, max_value=20)), lists(models(User), max_size=20)) def test_can_add_users_up_to_collaborator_limit(self, project, collaborators): for c in collaborators: if project.at_collaboration_limit(): with self.assertRaises(LimitReached): project.add_user(c) self.assertFalse(project.team_contains(c)) else: project.add_user(c) self.assertTrue(project.team_contains(c))

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class TestProjectManagement(TestCase): @given( models(Project, collaborator_limit=integers(min_value=0, max_value=20)), lists(models(User), max_size=20)) def test_can_add_users_up_to_collaborator_limit(self, project, collaborators): for c in collaborators: if project.at_collaboration_limit(): with self.assertRaises(LimitReached): project.add_user(c) self.assertFalse(project.team_contains(c)) else: project.add_user(c) self.assertTrue(project.team_contains(c))

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class TestProjectManagement(TestCase): @given( models(Project, collaborator_limit=integers(min_value=0, max_value=20)), lists(models(User), max_size=20)) def test_can_add_users_up_to_collaborator_limit(self, project, collaborators): for c in collaborators: if project.at_collaboration_limit(): with self.assertRaises(LimitReached): project.add_user(c) self.assertFalse(project.team_contains(c)) else: project.add_user(c) self.assertTrue(project.team_contains(c))

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class TestProjectManagement(TestCase): @given( models(Project, collaborator_limit=integers(min_value=0, max_value=20)), lists(models(User), max_size=20)) def test_can_add_users_up_to_collaborator_limit(self, project, collaborators): for c in collaborators: if project.at_collaboration_limit(): with self.assertRaises(LimitReached): project.add_user(c) self.assertFalse(project.team_contains(c)) else: project.add_user(c) self.assertTrue(project.team_contains(c))

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Falsifying example: test_can_add_users_up_to_collaborator_limit( self=TestProjectManagement(), project=Project('', 1), collaborators=[ User([email protected]), User([email protected]) ] ) Traceback (most recent call last): ... raise LimitReached() manager.models.LimitReached

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Property based testing is more complicated, yet more valuable

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Django test code coverage is 75%

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Deceptive metric

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High coverage != high quality

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Mutation testing available Python implementation: mutpy

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mut.py --target node --unit-test test_node target unit test

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if foo and bar: do_this() target unit test

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if foo and bar: do_this() if foo or bar: do_this() mutant unit test

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mutant killed

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mutant killed mutant survived

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AOR - arithmetic operator replacement BCR - break continue replacement COI - conditional operator insertion CRP - constant replacement DDL - decorator deletion LOR - logical operator replacement

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[*] Start mutation process: - targets: django.utils.encoding - tests: tests.utils_tests.test_encoding [*] 10 tests passed: - tests.utils_tests.test_encoding [0.00533 s] [*] Start mutants generation and execution: ... [*] Mutation score [12.19066 s]: 32.1% - all: 88 - killed: 24 (27.3%) - survived: 55 (62.5%) - incompetent: 7 (8.0%) - timeout: 2 (2.3%)

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[*] Start mutation process: - targets: django.utils.encoding - tests: tests.utils_tests.test_encoding [*] 10 tests passed: - tests.utils_tests.test_encoding [0.00533 s] [*] Start mutants generation and execution: ... [*] Mutation score [12.19066 s]: 32.1% - all: 88 - killed: 24 (27.3%) - survived: 55 (62.5%) - incompetent: 7 (8.0%) - timeout: 2 (2.3%)

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Django duration utils mutation score is 89%

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Django duration utils mutation score is 89% and the coverage is 100%

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Django encoding utils mutation score is 64%

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Django encoding utils mutation score is 64% while the coverage is 100%

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django Testing tutorial

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my_app ├── __init__.py ├── admin.py ├── migrations │ └── __init__.py ├── models.py ├── tests.py └── views.py

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my_app ├── __init__.py ├── admin.py ├── migrations │ └── __init__.py ├── models.py ├── tests.py └── views.py

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When testing, more is better

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# of tests total execution time

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slow tests, slow feedback loop

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7 tips on how to speed up your tests

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7 tips on how to speed up your tests #4 will shock you

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1. use MD5PasswordHasher

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1. use MD5PasswordHasher 2. have more SimpleTestCase

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1. use MD5PasswordHasher 2. have more SimpleTestCase 3. use setUpTestData()

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1. use MD5PasswordHasher 2. have more SimpleTestCase 3. use setUpTestData() 4. use mocks EVERYWHERE

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1. use MD5PasswordHasher 2. have more SimpleTestCase 3. use setUpTestData() 4. use mocks EVERYWHERE

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1. use MD5PasswordHasher 2. have more SimpleTestCase 3. use setUpTestData() 4. use mocks EVERYWHERE 5. be vigilant of what gets created in setUp()

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1. use MD5PasswordHasher 2. have more SimpleTestCase 3. use setUpTestData() 4. use mocks EVERYWHERE 5. be vigilant of what gets created in setUp() 6. don’t save model objects if not necessary

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1. use MD5PasswordHasher 2. have more SimpleTestCase 3. use setUpTestData() 4. use mocks EVERYWHERE 5. be vigilant of what gets created in setUp() 6. don’t save model objects if not necessary 7. isolate unit tests

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1. use MD5PasswordHasher 2. have more SimpleTestCase 3. use setUpTestData() 4. use mocks EVERYWHERE 5. be vigilant of what gets created in setUp() 6. don’t save model objects if not necessary 7. isolate unit tests

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class SimpleTest(TestCase): def setUp(self): for _ in range(10): Robot.objects.create() 5. be vigilant of what gets created in setUp()

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class SimpleTest(TestCase): def setUp(self): for _ in range(10): Robot.objects.create() 5. be vigilant of what gets created in setUp()

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6. don’t save model objects if not necessary

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6. don’t save model objects if not necessary Robot.objects.create() instead of

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6. don’t save model objects if not necessary Robot.objects.create() Robot() instead of maybe do

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6. don’t save model objects if not necessary Robot.objects.create() Robot() RobotFactory.build() instead of maybe do or

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6. don’t save model objects if not necessary Robot.objects.create() Robot() RobotFactory.build() RobotFactory.stub() instead of maybe do or or

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6. don’t save model objects if not necessary Robot.objects.create() Robot() RobotFactory.build() RobotFactory.stub() factory boy instead of maybe do or or }

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7. isolate unit tests

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7. isolate unit tests

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7. isolate unit tests

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7. isolate unit tests unit tests functional tests

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7. isolate unit tests unit tests functional tests ./manage.py test --tag=unit

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Ugh, taxes!

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Product ProductQuestionnaire name ingredients price product category drink_category food_category has_decorations is_coated_in_chocolate is_warm is_cold

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Production code Test

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class ProductQuestionnaireCreate(CreateView): def form_valid(self, form): if is_biscuit and is_coated_in_chocolate: set_vat_20() return super().form_valid(form) class ProductQuestionnaireCreateTestCase(TestCase): def test_20p_vat_if_coated_in_chocolate_biscuit(self): product = ProductFactory() response = self.client.post(self.url, {'q1': 'a1', 'q2': 'a2'}) product.refresh_from_db() self.assertEqual(product.vat, 20) solution #1

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class ProductQuestionnaireCreate(CreateView): def form_valid(self, form): if is_biscuit and is_coated_in_chocolate: set_vat_20() return super().form_valid(form) class ProductQuestionnaireCreateTestCase(TestCase): def test_20p_vat_if_coated_in_chocolate_biscuit(self): product = ProductFactory() response = self.client.post(self.url, {'q1': 'a1', 'q2': 'a2'}) product.refresh_from_db() self.assertEqual(product.vat, 20) solution #1

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class ProductQuestionnaireCreate(CreateView): def form_valid(self, form): return super().form_valid(form)

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class ProductQuestionnaireCreateTestCase(TestCase): def test_20p_vat_if_coated_in_chocolate_biscuit(self): def test_0p_vat_if_baguette(self): def test_0p_vat_if_flapjack(self): def test_20p_vat_if_cereal_bar(self):

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To test if I need to pay 20% VAT for biscuits coated in chocolate, I need to: go through the router interact with database send input to receive output

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Mocks are not a solution

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class ProductQuestionnaireForm(forms.ModelForm): def save(self, commit=True): instance = super().save(commit) if is_biscuit and is_coated_in_chocolate: set_vat_20() return instance solution #2 class ProductQuestionnaireFormTestCase(TestCase): def test_20p_vat_if_coated_in_chocolate_biscuit(self): product = ProductFactory() form = ProductQuestionnaireForm(data={'k1': 'v1', 'k2': 'v2'}) self.assertTrue(form.is_valid()) form.save() product.refresh_from_db() self.assertEqual(product.vat, 20)

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class ProductQuestionnaireForm(forms.ModelForm): def save(self, commit=True): instance = super().save(commit) if is_biscuit and is_coated_in_chocolate: set_vat_20() return instance solution #2 class ProductQuestionnaireFormTestCase(TestCase): def test_20p_vat_if_coated_in_chocolate_biscuit(self): product = ProductFactory() form = ProductQuestionnaireForm(data={'k1': 'v1', 'k2': 'v2'}) self.assertTrue(form.is_valid()) form.save() product.refresh_from_db() self.assertEqual(product.vat, 20)

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To test if I need to pay 20% VAT for biscuits coated in chocolate, I need to: go through the router interact with database send input to receive output

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solution #3 class VATCalculator(object): def calculate_vat(self, **kwargs): if is_biscuit and is_coated_in_chocolate: return 20 class VATCalculatorTestCase(SimpleTestCase): def test_20p_vat_if_coated_in_chocolate_biscuit(self): calc = VATCalculator() self.assertEqual(calc.calculate_vat( is_biscuit=True, is_coated_in_choco=True ), 20)

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To test if I need to pay 20% VAT for biscuits coated in chocolate, I need to: go through the router interact with database send input to receive output

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reusability testability extensibility

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No content

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Tests have more in them than we think

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Happy testing and big bear hug thanks!