Advanced testing topics¶
The request factory¶
The RequestFactory
shares the same API as
the test client. However, instead of behaving like a browser, the
RequestFactory provides a way to generate a request instance that can
be used as the first argument to any view. This means you can test a
view function the same way as you would test any other function – as
a black box, with exactly known inputs, testing for specific outputs.
The API for the RequestFactory
is a slightly
restricted subset of the test client API:
- It only has access to the HTTP methods
get()
,post()
,put()
,delete()
,head()
,options()
, andtrace()
. - These methods accept all the same arguments except for
follow
. Since this is just a factory for producing requests, it’s up to you to handle the response. - It does not support middleware. Session and authentication attributes must be supplied by the test itself if required for the view to function properly.
Example¶
The following is a unit test using the request factory:
from django.contrib.auth.models import AnonymousUser, User
from django.test import RequestFactory, TestCase
from .views import MyView, my_view
class SimpleTest(TestCase):
def setUp(self):
# Every test needs access to the request factory.
self.factory = RequestFactory()
self.user = User.objects.create_user(
username='jacob', email='jacob@…', password='top_secret')
def test_details(self):
# Create an instance of a GET request.
request = self.factory.get('/customer/details')
# Recall that middleware are not supported. You can simulate a
# logged-in user by setting request.user manually.
request.user = self.user
# Or you can simulate an anonymous user by setting request.user to
# an AnonymousUser instance.
request.user = AnonymousUser()
# Test my_view() as if it were deployed at /customer/details
response = my_view(request)
# Use this syntax for class-based views.
response = MyView.as_view()(request)
self.assertEqual(response.status_code, 200)
AsyncRequestFactory¶
RequestFactory
creates WSGI-like requests. If you want to create ASGI-like
requests, including having a correct ASGI scope
, you can instead use
django.test.AsyncRequestFactory
.
This class is directly API-compatible with RequestFactory
, with the only
difference being that it returns ASGIRequest
instances rather than
WSGIRequest
instances. All of its methods are still synchronous callables.
Testing class-based views¶
In order to test class-based views outside of the request/response cycle you
must ensure that they are configured correctly, by calling
setup()
after instantiation.
For example, assuming the following class-based view:
from django.views.generic import TemplateView
class HomeView(TemplateView):
template_name = 'myapp/home.html'
def get_context_data(self, **kwargs):
kwargs['environment'] = 'Production'
return super().get_context_data(**kwargs)
You may directly test the get_context_data()
method by first instantiating
the view, then passing a request
to setup()
, before proceeding with
your test’s code:
from django.test import RequestFactory, TestCase
from .views import HomeView
class HomePageTest(TestCase):
def test_environment_set_in_context(self):
request = RequestFactory().get('/')
view = HomeView()
view.setup(request)
context = view.get_context_data()
self.assertIn('environment', context)
Tests and multiple host names¶
The ALLOWED_HOSTS
setting is validated when running tests. This
allows the test client to differentiate between internal and external URLs.
Projects that support multitenancy or otherwise alter business logic based on
the request’s host and use custom host names in tests must include those hosts
in ALLOWED_HOSTS
.
The first option to do so is to add the hosts to your settings file. For example, the test suite for docs.djangoproject.com includes the following:
from django.test import TestCase
class SearchFormTestCase(TestCase):
def test_empty_get(self):
response = self.client.get('/en/dev/search/', HTTP_HOST='docs.djangoproject.dev:8000')
self.assertEqual(response.status_code, 200)
and the settings file includes a list of the domains supported by the project:
ALLOWED_HOSTS = [
'www.djangoproject.dev',
'docs.djangoproject.dev',
...
]
Another option is to add the required hosts to ALLOWED_HOSTS
using
override_settings()
or
modify_settings()
. This option may be
preferable in standalone apps that can’t package their own settings file or
for projects where the list of domains is not static (e.g., subdomains for
multitenancy). For example, you could write a test for the domain
http://otherserver/
as follows:
from django.test import TestCase, override_settings
class MultiDomainTestCase(TestCase):
@override_settings(ALLOWED_HOSTS=['otherserver'])
def test_other_domain(self):
response = self.client.get('http://otherserver/foo/bar/')
Disabling ALLOWED_HOSTS
checking (ALLOWED_HOSTS = ['*']
) when
running tests prevents the test client from raising a helpful error message if
you follow a redirect to an external URL.
Tests and multiple databases¶
Testing primary/replica configurations¶
If you’re testing a multiple database configuration with primary/replica (referred to as master/slave by some databases) replication, this strategy of creating test databases poses a problem. When the test databases are created, there won’t be any replication, and as a result, data created on the primary won’t be seen on the replica.
To compensate for this, Django allows you to define that a database is a test mirror. Consider the following (simplified) example database configuration:
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.mysql',
'NAME': 'myproject',
'HOST': 'dbprimary',
# ... plus some other settings
},
'replica': {
'ENGINE': 'django.db.backends.mysql',
'NAME': 'myproject',
'HOST': 'dbreplica',
'TEST': {
'MIRROR': 'default',
},
# ... plus some other settings
}
}
In this setup, we have two database servers: dbprimary
, described
by the database alias default
, and dbreplica
described by the
alias replica
. As you might expect, dbreplica
has been configured
by the database administrator as a read replica of dbprimary
, so in
normal activity, any write to default
will appear on replica
.
If Django created two independent test databases, this would break any
tests that expected replication to occur. However, the replica
database has been configured as a test mirror (using the
MIRROR
test setting), indicating that under
testing, replica
should be treated as a mirror of default
.
When the test environment is configured, a test version of replica
will not be created. Instead the connection to replica
will be redirected to point at default
. As a result, writes to
default
will appear on replica
– but because they are actually
the same database, not because there is data replication between the
two databases.
Controlling creation order for test databases¶
By default, Django will assume all databases depend on the default
database and therefore always create the default
database first.
However, no guarantees are made on the creation order of any other
databases in your test setup.
If your database configuration requires a specific creation order, you
can specify the dependencies that exist using the DEPENDENCIES
test setting. Consider the following (simplified)
example database configuration:
DATABASES = {
'default': {
# ... db settings
'TEST': {
'DEPENDENCIES': ['diamonds'],
},
},
'diamonds': {
# ... db settings
'TEST': {
'DEPENDENCIES': [],
},
},
'clubs': {
# ... db settings
'TEST': {
'DEPENDENCIES': ['diamonds'],
},
},
'spades': {
# ... db settings
'TEST': {
'DEPENDENCIES': ['diamonds', 'hearts'],
},
},
'hearts': {
# ... db settings
'TEST': {
'DEPENDENCIES': ['diamonds', 'clubs'],
},
}
}
Under this configuration, the diamonds
database will be created first,
as it is the only database alias without dependencies. The default
and
clubs
alias will be created next (although the order of creation of this
pair is not guaranteed), then hearts
, and finally spades
.
If there are any circular dependencies in the DEPENDENCIES
definition, an
ImproperlyConfigured
exception will be raised.
Advanced features of TransactionTestCase
¶
-
TransactionTestCase.
available_apps
¶ Warning
This attribute is a private API. It may be changed or removed without a deprecation period in the future, for instance to accommodate changes in application loading.
It’s used to optimize Django’s own test suite, which contains hundreds of models but no relations between models in different applications.
By default,
available_apps
is set toNone
. After each test, Django callsflush
to reset the database state. This empties all tables and emits thepost_migrate
signal, which recreates one content type and four permissions for each model. This operation gets expensive proportionally to the number of models.Setting
available_apps
to a list of applications instructs Django to behave as if only the models from these applications were available. The behavior ofTransactionTestCase
changes as follows:post_migrate
is fired before each test to create the content types and permissions for each model in available apps, in case they’re missing.- After each test, Django empties only tables corresponding to models in
available apps. However, at the database level, truncation may cascade to
related models in unavailable apps. Furthermore
post_migrate
isn’t fired; it will be fired by the nextTransactionTestCase
, after the correct set of applications is selected.
Since the database isn’t fully flushed, if a test creates instances of models not included in
available_apps
, they will leak and they may cause unrelated tests to fail. Be careful with tests that use sessions; the default session engine stores them in the database.Since
post_migrate
isn’t emitted after flushing the database, its state after aTransactionTestCase
isn’t the same as after aTestCase
: it’s missing the rows created by listeners topost_migrate
. Considering the order in which tests are executed, this isn’t an issue, provided either allTransactionTestCase
in a given test suite declareavailable_apps
, or none of them.available_apps
is mandatory in Django’s own test suite.
-
TransactionTestCase.
reset_sequences
¶ Setting
reset_sequences = True
on aTransactionTestCase
will make sure sequences are always reset before the test run:class TestsThatDependsOnPrimaryKeySequences(TransactionTestCase): reset_sequences = True def test_animal_pk(self): lion = Animal.objects.create(name="lion", sound="roar") # lion.pk is guaranteed to always be 1 self.assertEqual(lion.pk, 1)
Unless you are explicitly testing primary keys sequence numbers, it is recommended that you do not hard code primary key values in tests.
Using
reset_sequences = True
will slow down the test, since the primary key reset is a relatively expensive database operation.
Enforce running test classes sequentially¶
If you have test classes that cannot be run in parallel (e.g. because they
share a common resource), you can use django.test.testcases.SerializeMixin
to run them sequentially. This mixin uses a filesystem lockfile
.
For example, you can use __file__
to determine that all test classes in the
same file that inherit from SerializeMixin
will run sequentially:
import os
from django.test import TestCase
from django.test.testcases import SerializeMixin
class ImageTestCaseMixin(SerializeMixin):
lockfile = __file__
def setUp(self):
self.filename = os.path.join(temp_storage_dir, 'my_file.png')
self.file = create_file(self.filename)
class RemoveImageTests(ImageTestCaseMixin, TestCase):
def test_remove_image(self):
os.remove(self.filename)
self.assertFalse(os.path.exists(self.filename))
class ResizeImageTests(ImageTestCaseMixin, TestCase):
def test_resize_image(self):
resize_image(self.file, (48, 48))
self.assertEqual(get_image_size(self.file), (48, 48))
Using the Django test runner to test reusable applications¶
If you are writing a reusable application you may want to use the Django test runner to run your own test suite and thus benefit from the Django testing infrastructure.
A common practice is a tests directory next to the application code, with the following structure:
runtests.py
polls/
__init__.py
models.py
...
tests/
__init__.py
models.py
test_settings.py
tests.py
Let’s take a look inside a couple of those files:
#!/usr/bin/env python
import os
import sys
import django
from django.conf import settings
from django.test.utils import get_runner
if __name__ == "__main__":
os.environ['DJANGO_SETTINGS_MODULE'] = 'tests.test_settings'
django.setup()
TestRunner = get_runner(settings)
test_runner = TestRunner()
failures = test_runner.run_tests(["tests"])
sys.exit(bool(failures))
This is the script that you invoke to run the test suite. It sets up the Django environment, creates the test database and runs the tests.
For the sake of clarity, this example contains only the bare minimum necessary to use the Django test runner. You may want to add command-line options for controlling verbosity, passing in specific test labels to run, etc.
SECRET_KEY = 'fake-key'
INSTALLED_APPS = [
"tests",
]
This file contains the Django settings required to run your app’s tests.
Again, this is a minimal example; your tests may require additional settings to run.
Since the tests package is included in INSTALLED_APPS
when
running your tests, you can define test-only models in its models.py
file.
Using different testing frameworks¶
Clearly, unittest
is not the only Python testing framework. While Django
doesn’t provide explicit support for alternative frameworks, it does provide a
way to invoke tests constructed for an alternative framework as if they were
normal Django tests.
When you run ./manage.py test
, Django looks at the TEST_RUNNER
setting to determine what to do. By default, TEST_RUNNER
points to
'django.test.runner.DiscoverRunner'
. This class defines the default Django
testing behavior. This behavior involves:
- Performing global pre-test setup.
- Looking for tests in any file below the current directory whose name matches
the pattern
test*.py
. - Creating the test databases.
- Running
migrate
to install models and initial data into the test databases. - Running the system checks.
- Running the tests that were found.
- Destroying the test databases.
- Performing global post-test teardown.
If you define your own test runner class and point TEST_RUNNER
at
that class, Django will execute your test runner whenever you run
./manage.py test
. In this way, it is possible to use any test framework
that can be executed from Python code, or to modify the Django test execution
process to satisfy whatever testing requirements you may have.
Defining a test runner¶
A test runner is a class defining a run_tests()
method. Django ships
with a DiscoverRunner
class that defines the default Django testing
behavior. This class defines the run_tests()
entry point, plus a
selection of other methods that are used by run_tests()
to set up, execute
and tear down the test suite.
-
class
DiscoverRunner
(pattern='test*.py', top_level=None, verbosity=1, interactive=True, failfast=False, keepdb=False, reverse=False, debug_mode=False, debug_sql=False, parallel=0, tags=None, exclude_tags=None, test_name_patterns=None, pdb=False, buffer=False, enable_faulthandler=True, timing=True, **kwargs)[source]¶ DiscoverRunner
will search for tests in any file matchingpattern
.top_level
can be used to specify the directory containing your top-level Python modules. Usually Django can figure this out automatically, so it’s not necessary to specify this option. If specified, it should generally be the directory containing yourmanage.py
file.verbosity
determines the amount of notification and debug information that will be printed to the console;0
is no output,1
is normal output, and2
is verbose output.If
interactive
isTrue
, the test suite has permission to ask the user for instructions when the test suite is executed. An example of this behavior would be asking for permission to delete an existing test database. Ifinteractive
isFalse
, the test suite must be able to run without any manual intervention.If
failfast
isTrue
, the test suite will stop running after the first test failure is detected.If
keepdb
isTrue
, the test suite will use the existing database, or create one if necessary. IfFalse
, a new database will be created, prompting the user to remove the existing one, if present.If
reverse
isTrue
, test cases will be executed in the opposite order. This could be useful to debug tests that aren’t properly isolated and have side effects. Grouping by test class is preserved when using this option.debug_mode
specifies what theDEBUG
setting should be set to prior to running tests.parallel
specifies the number of processes. Ifparallel
is greater than1
, the test suite will run inparallel
processes. If there are fewer test cases than configured processes, Django will reduce the number of processes accordingly. Each process gets its own database. This option requires the third-partytblib
package to display tracebacks correctly.tags
can be used to specify a set of tags for filtering tests. May be combined withexclude_tags
.exclude_tags
can be used to specify a set of tags for excluding tests. May be combined withtags
.If
debug_sql
isTrue
, failing test cases will output SQL queries logged to the django.db.backends logger as well as the traceback. Ifverbosity
is2
, then queries in all tests are output.test_name_patterns
can be used to specify a set of patterns for filtering test methods and classes by their names.If
pdb
isTrue
, a debugger (pdb
oripdb
) will be spawned at each test error or failure.If
buffer
isTrue
, outputs from passing tests will be discarded.If
enable_faulthandler
isTrue
,faulthandler
will be enabled.If
timing
isTrue
, test timings, including database setup and total run time, will be shown.Django may, from time to time, extend the capabilities of the test runner by adding new arguments. The
**kwargs
declaration allows for this expansion. If you subclassDiscoverRunner
or write your own test runner, ensure it accepts**kwargs
.Your test runner may also define additional command-line options. Create or override an
add_arguments(cls, parser)
class method and add custom arguments by callingparser.add_argument()
inside the method, so that thetest
command will be able to use those arguments.New in Django 3.1:The
buffer
argument was added.New in Django 3.2:The
enable_faulthandler
andtiming
arguments were added.
Attributes¶
-
DiscoverRunner.
test_suite
¶ The class used to build the test suite. By default it is set to
unittest.TestSuite
. This can be overridden if you wish to implement different logic for collecting tests.
-
DiscoverRunner.
test_runner
¶ This is the class of the low-level test runner which is used to execute the individual tests and format the results. By default it is set to
unittest.TextTestRunner
. Despite the unfortunate similarity in naming conventions, this is not the same type of class asDiscoverRunner
, which covers a broader set of responsibilities. You can override this attribute to modify the way tests are run and reported.
-
DiscoverRunner.
test_loader
¶ This is the class that loads tests, whether from TestCases or modules or otherwise and bundles them into test suites for the runner to execute. By default it is set to
unittest.defaultTestLoader
. You can override this attribute if your tests are going to be loaded in unusual ways.
Methods¶
-
DiscoverRunner.
run_tests
(test_labels, extra_tests=None, **kwargs)[source]¶ Run the test suite.
test_labels
allows you to specify which tests to run and supports several formats (seeDiscoverRunner.build_suite()
for a list of supported formats).extra_tests
is a list of extraTestCase
instances to add to the suite that is executed by the test runner. These extra tests are run in addition to those discovered in the modules listed intest_labels
.This method should return the number of tests that failed.
-
classmethod
DiscoverRunner.
add_arguments
(parser)[source]¶ Override this class method to add custom arguments accepted by the
test
management command. Seeargparse.ArgumentParser.add_argument()
for details about adding arguments to a parser.
-
DiscoverRunner.
setup_test_environment
(**kwargs)[source]¶ Sets up the test environment by calling
setup_test_environment()
and settingDEBUG
toself.debug_mode
(defaults toFalse
).
-
DiscoverRunner.
build_suite
(test_labels=None, extra_tests=None, **kwargs)[source]¶ Constructs a test suite that matches the test labels provided.
test_labels
is a list of strings describing the tests to be run. A test label can take one of four forms:path.to.test_module.TestCase.test_method
– Run a single test method in a test case.path.to.test_module.TestCase
– Run all the test methods in a test case.path.to.module
– Search for and run all tests in the named Python package or module.path/to/directory
– Search for and run all tests below the named directory.
If
test_labels
has a value ofNone
, the test runner will search for tests in all files below the current directory whose names match itspattern
(see above).extra_tests
is a list of extraTestCase
instances to add to the suite that is executed by the test runner. These extra tests are run in addition to those discovered in the modules listed intest_labels
.Returns a
TestSuite
instance ready to be run.
-
DiscoverRunner.
setup_databases
(**kwargs)[source]¶ Creates the test databases by calling
setup_databases()
.
-
DiscoverRunner.
run_checks
(databases)[source]¶ Runs the system checks on the test
databases
.New in Django 3.1:The
databases
parameter was added.
-
DiscoverRunner.
run_suite
(suite, **kwargs)[source]¶ Runs the test suite.
Returns the result produced by the running the test suite.
-
DiscoverRunner.
get_test_runner_kwargs
()[source]¶ Returns the keyword arguments to instantiate the
DiscoverRunner.test_runner
with.
-
DiscoverRunner.
teardown_databases
(old_config, **kwargs)[source]¶ Destroys the test databases, restoring pre-test conditions by calling
teardown_databases()
.
Testing utilities¶
django.test.utils
¶
To assist in the creation of your own test runner, Django provides a number of
utility methods in the django.test.utils
module.
-
setup_test_environment
(debug=None)[source]¶ Performs global pre-test setup, such as installing instrumentation for the template rendering system and setting up the dummy email outbox.
If
debug
isn’tNone
, theDEBUG
setting is updated to its value.
-
teardown_test_environment
()[source]¶ Performs global post-test teardown, such as removing instrumentation from the template system and restoring normal email services.
-
setup_databases
(verbosity, interactive, *, time_keeper=None, keepdb=False, debug_sql=False, parallel=0, aliases=None, **kwargs)[source]¶ Creates the test databases.
Returns a data structure that provides enough detail to undo the changes that have been made. This data will be provided to the
teardown_databases()
function at the conclusion of testing.The
aliases
argument determines whichDATABASES
aliases test databases should be setup for. If it’s not provided, it defaults to all ofDATABASES
aliases.Changed in Django 3.2:The
time_keeper
kwarg was added, and all kwargs were made keyword-only.
-
teardown_databases
(old_config, parallel=0, keepdb=False)[source]¶ Destroys the test databases, restoring pre-test conditions.
old_config
is a data structure defining the changes in the database configuration that need to be reversed. It’s the return value of thesetup_databases()
method.
django.db.connection.creation
¶
The creation module of the database backend also provides some utilities that can be useful during testing.
-
create_test_db
(verbosity=1, autoclobber=False, serialize=True, keepdb=False)¶ Creates a new test database and runs
migrate
against it.verbosity
has the same behavior as inrun_tests()
.autoclobber
describes the behavior that will occur if a database with the same name as the test database is discovered:- If
autoclobber
isFalse
, the user will be asked to approve destroying the existing database.sys.exit
is called if the user does not approve. - If autoclobber is
True
, the database will be destroyed without consulting the user.
serialize
determines if Django serializes the database into an in-memory JSON string before running tests (used to restore the database state between tests if you don’t have transactions). You can set this toFalse
to speed up creation time if you don’t have any test classes with serialized_rollback=True.If you are using the default test runner, you can control this with the the
SERIALIZE
entry in theTEST
dictionary.keepdb
determines if the test run should use an existing database, or create a new one. IfTrue
, the existing database will be used, or created if not present. IfFalse
, a new database will be created, prompting the user to remove the existing one, if present.Returns the name of the test database that it created.
create_test_db()
has the side effect of modifying the value ofNAME
inDATABASES
to match the name of the test database.- If
-
destroy_test_db
(old_database_name, verbosity=1, keepdb=False)¶ Destroys the database whose name is the value of
NAME
inDATABASES
, and setsNAME
to the value ofold_database_name
.The
verbosity
argument has the same behavior as forDiscoverRunner
.If the
keepdb
argument isTrue
, then the connection to the database will be closed, but the database will not be destroyed.
Integration with coverage.py
¶
Code coverage describes how much source code has been tested. It shows which parts of your code are being exercised by tests and which are not. It’s an important part of testing applications, so it’s strongly recommended to check the coverage of your tests.
Django can be easily integrated with coverage.py, a tool for measuring code
coverage of Python programs. First, install coverage.py. Next, run the
following from your project folder containing manage.py
:
coverage run --source='.' manage.py test myapp
This runs your tests and collects coverage data of the executed files in your project. You can see a report of this data by typing following command:
coverage report
Note that some Django code was executed while running tests, but it is not
listed here because of the source
flag passed to the previous command.
For more options like annotated HTML listings detailing missed lines, see the coverage.py docs.