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tools.txt
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tools.txt
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=============
Testing tools
=============
.. currentmodule:: django.test
Django provides a small set of tools that come in handy when writing tests.
.. _test-client:
The test client
===============
The test client is a Python class that acts as a dummy web browser, allowing
you to test your views and interact with your Django-powered application
programmatically.
Some of the things you can do with the test client are:
* Simulate GET and POST requests on a URL and observe the response --
everything from low-level HTTP (result headers and status codes) to
page content.
* See the chain of redirects (if any) and check the URL and status code at
each step.
* Test that a given request is rendered by a given Django template, with
a template context that contains certain values.
Note that the test client is not intended to be a replacement for Selenium_ or
other "in-browser" frameworks. Django's test client has a different focus. In
short:
* Use Django's test client to establish that the correct template is being
rendered and that the template is passed the correct context data.
* Use :class:`~django.test.RequestFactory` to test view functions directly,
bypassing the routing and middleware layers.
* Use in-browser frameworks like Selenium_ to test *rendered* HTML and the
*behavior* of web pages, namely JavaScript functionality. Django also
provides special support for those frameworks; see the section on
:class:`~django.test.LiveServerTestCase` for more details.
A comprehensive test suite should use a combination of all of these test types.
Overview and a quick example
----------------------------
To use the test client, instantiate ``django.test.Client`` and retrieve
web pages:
.. code-block:: pycon
>>> from django.test import Client
>>> c = Client()
>>> response = c.post("/login/", {"username": "john", "password": "smith"})
>>> response.status_code
200
>>> response = c.get("/customer/details/")
>>> response.content
b'<!DOCTYPE html...'
As this example suggests, you can instantiate ``Client`` from within a session
of the Python interactive interpreter.
Note a few important things about how the test client works:
* The test client does *not* require the web server to be running. In fact,
it will run just fine with no web server running at all! That's because
it avoids the overhead of HTTP and deals directly with the Django
framework. This helps make the unit tests run quickly.
* When retrieving pages, remember to specify the *path* of the URL, not the
whole domain. For example, this is correct:
.. code-block:: pycon
>>> c.get("/login/")
This is incorrect:
.. code-block:: pycon
>>> c.get("https://www.example.com/login/")
The test client is not capable of retrieving web pages that are not
powered by your Django project. If you need to retrieve other web pages,
use a Python standard library module such as :mod:`urllib`.
* To resolve URLs, the test client uses whatever URLconf is pointed-to by
your :setting:`ROOT_URLCONF` setting.
* Although the above example would work in the Python interactive
interpreter, some of the test client's functionality, notably the
template-related functionality, is only available *while tests are
running*.
The reason for this is that Django's test runner performs a bit of black
magic in order to determine which template was loaded by a given view.
This black magic (essentially a patching of Django's template system in
memory) only happens during test running.
* By default, the test client will disable any CSRF checks
performed by your site.
If, for some reason, you *want* the test client to perform CSRF
checks, you can create an instance of the test client that
enforces CSRF checks. To do this, pass in the
``enforce_csrf_checks`` argument when you construct your
client:
.. code-block:: pycon
>>> from django.test import Client
>>> csrf_client = Client(enforce_csrf_checks=True)
Making requests
---------------
Use the ``django.test.Client`` class to make requests.
.. class:: Client(enforce_csrf_checks=False, raise_request_exception=True, json_encoder=DjangoJSONEncoder, *, headers=None, query_params=None, **defaults)
A testing HTTP client. Takes several arguments that can customize behavior.
``headers`` allows you to specify default headers that will be sent with
every request. For example, to set a ``User-Agent`` header::
client = Client(headers={"user-agent": "curl/7.79.1"})
``query_params`` allows you to specify the default query string that will
be set on every request.
Arbitrary keyword arguments in ``**defaults`` set WSGI
:pep:`environ variables <3333#environ-variables>`. For example, to set the
script name::
client = Client(SCRIPT_NAME="/app/")
.. note::
Keyword arguments starting with a ``HTTP_`` prefix are set as headers,
but the ``headers`` parameter should be preferred for readability.
The values from the ``headers``, ``query_params``, and ``extra`` keyword
arguments passed to :meth:`~django.test.Client.get()`,
:meth:`~django.test.Client.post()`, etc. have precedence over
the defaults passed to the class constructor.
The ``enforce_csrf_checks`` argument can be used to test CSRF
protection (see above).
The ``raise_request_exception`` argument allows controlling whether or not
exceptions raised during the request should also be raised in the test.
Defaults to ``True``.
The ``json_encoder`` argument allows setting a custom JSON encoder for
the JSON serialization that's described in :meth:`post`.
.. versionchanged:: 5.1
The ``query_params`` argument was added.
Once you have a ``Client`` instance, you can call any of the following
methods:
.. method:: Client.get(path, data=None, follow=False, secure=False, *, headers=None, query_params=None, **extra)
Makes a GET request on the provided ``path`` and returns a ``Response``
object, which is documented below.
The key-value pairs in the ``query_params`` dictionary are used to set
query strings. For example:
.. code-block:: pycon
>>> c = Client()
>>> c.get("/customers/details/", query_params={"name": "fred", "age": 7})
...will result in the evaluation of a GET request equivalent to:
.. code-block:: text
/customers/details/?name=fred&age=7
It is also possible to pass these parameters into the ``data``
parameter. However, ``query_params`` is preferred as it works for any
HTTP method.
The ``headers`` parameter can be used to specify headers to be sent in
the request. For example:
.. code-block:: pycon
>>> c = Client()
>>> c.get(
... "/customers/details/",
... query_params={"name": "fred", "age": 7},
... headers={"accept": "application/json"},
... )
...will send the HTTP header ``HTTP_ACCEPT`` to the details view, which
is a good way to test code paths that use the
:meth:`django.http.HttpRequest.accepts()` method.
Arbitrary keyword arguments set WSGI
:pep:`environ variables <3333#environ-variables>`. For example, headers
to set the script name:
.. code-block:: pycon
>>> c = Client()
>>> c.get("/", SCRIPT_NAME="/app/")
If you already have the GET arguments in URL-encoded form, you can
use that encoding instead of using the data argument. For example,
the previous GET request could also be posed as:
.. code-block:: pycon
>>> c = Client()
>>> c.get("/customers/details/?name=fred&age=7")
If you provide a URL with both an encoded GET data and either a
query_params or data argument these arguments will take precedence.
If you set ``follow`` to ``True`` the client will follow any redirects
and a ``redirect_chain`` attribute will be set in the response object
containing tuples of the intermediate urls and status codes.
If you had a URL ``/redirect_me/`` that redirected to ``/next/``, that
redirected to ``/final/``, this is what you'd see:
.. code-block:: pycon
>>> response = c.get("/redirect_me/", follow=True)
>>> response.redirect_chain
[('http://testserver/next/', 302), ('http://testserver/final/', 302)]
If you set ``secure`` to ``True`` the client will emulate an HTTPS
request.
.. versionchanged:: 5.1
The ``query_params`` argument was added.
.. method:: Client.post(path, data=None, content_type=MULTIPART_CONTENT, follow=False, secure=False, *, headers=None, query_params=None, **extra)
Makes a POST request on the provided ``path`` and returns a
``Response`` object, which is documented below.
The key-value pairs in the ``data`` dictionary are used to submit POST
data. For example:
.. code-block:: pycon
>>> c = Client()
>>> c.post("/login/", {"name": "fred", "passwd": "secret"})
...will result in the evaluation of a POST request to this URL:
.. code-block:: text
/login/
...with this POST data:
.. code-block:: text
name=fred&passwd=secret
If you provide ``content_type`` as :mimetype:`application/json`, the
``data`` is serialized using :func:`json.dumps` if it's a dict, list,
or tuple. Serialization is performed with
:class:`~django.core.serializers.json.DjangoJSONEncoder` by default,
and can be overridden by providing a ``json_encoder`` argument to
:class:`Client`. This serialization also happens for :meth:`put`,
:meth:`patch`, and :meth:`delete` requests.
If you provide any other ``content_type`` (e.g. :mimetype:`text/xml`
for an XML payload), the contents of ``data`` are sent as-is in the
POST request, using ``content_type`` in the HTTP ``Content-Type``
header.
If you don't provide a value for ``content_type``, the values in
``data`` will be transmitted with a content type of
:mimetype:`multipart/form-data`. In this case, the key-value pairs in
``data`` will be encoded as a multipart message and used to create the
POST data payload.
To submit multiple values for a given key -- for example, to specify
the selections for a ``<select multiple>`` -- provide the values as a
list or tuple for the required key. For example, this value of ``data``
would submit three selected values for the field named ``choices``::
{"choices": ["a", "b", "d"]}
Submitting files is a special case. To POST a file, you need only
provide the file field name as a key, and a file handle to the file you
wish to upload as a value. For example, if your form has fields
``name`` and ``attachment``, the latter a
:class:`~django.forms.FileField`:
.. code-block:: pycon
>>> c = Client()
>>> with open("wishlist.doc", "rb") as fp:
... c.post("/customers/wishes/", {"name": "fred", "attachment": fp})
...
You may also provide any file-like object (e.g., :class:`~io.StringIO` or
:class:`~io.BytesIO`) as a file handle. If you're uploading to an
:class:`~django.db.models.ImageField`, the object needs a ``name``
attribute that passes the
:data:`~django.core.validators.validate_image_file_extension` validator.
For example:
.. code-block:: pycon
>>> from io import BytesIO
>>> img = BytesIO(
... b"GIF89a\x01\x00\x01\x00\x00\x00\x00!\xf9\x04\x01\x00\x00\x00"
... b"\x00,\x00\x00\x00\x00\x01\x00\x01\x00\x00\x02\x01\x00\x00"
... )
>>> img.name = "myimage.gif"
Note that if you wish to use the same file handle for multiple
``post()`` calls then you will need to manually reset the file
pointer between posts. The easiest way to do this is to
manually close the file after it has been provided to
``post()``, as demonstrated above.
You should also ensure that the file is opened in a way that
allows the data to be read. If your file contains binary data
such as an image, this means you will need to open the file in
``rb`` (read binary) mode.
The ``headers``, ``query_params``, and ``extra`` parameters acts the
same as for :meth:`Client.get`.
If the URL you request with a POST contains encoded parameters, these
parameters will be made available in the request.GET data. For example,
if you were to make the request:
.. code-block:: pycon
>>> c.post(
... "/login/", {"name": "fred", "passwd": "secret"}, query_params={"visitor": "true"}
... )
... the view handling this request could interrogate request.POST
to retrieve the username and password, and could interrogate request.GET
to determine if the user was a visitor.
If you set ``follow`` to ``True`` the client will follow any redirects
and a ``redirect_chain`` attribute will be set in the response object
containing tuples of the intermediate urls and status codes.
If you set ``secure`` to ``True`` the client will emulate an HTTPS
request.
.. versionchanged:: 5.1
The ``query_params`` argument was added.
.. method:: Client.head(path, data=None, follow=False, secure=False, *, headers=None, query_params=None, **extra)
Makes a HEAD request on the provided ``path`` and returns a
``Response`` object. This method works just like :meth:`Client.get`,
including the ``follow``, ``secure``, ``headers``, ``query_params``,
and ``extra`` parameters, except it does not return a message body.
.. versionchanged:: 5.1
The ``query_params`` argument was added.
.. method:: Client.options(path, data='', content_type='application/octet-stream', follow=False, secure=False, *, headers=None, query_params=None, **extra)
Makes an OPTIONS request on the provided ``path`` and returns a
``Response`` object. Useful for testing RESTful interfaces.
When ``data`` is provided, it is used as the request body, and
a ``Content-Type`` header is set to ``content_type``.
The ``follow``, ``secure``, ``headers``, ``query_params``, and
``extra`` parameters act the same as for :meth:`Client.get`.
.. versionchanged:: 5.1
The ``query_params`` argument was added.
.. method:: Client.put(path, data='', content_type='application/octet-stream', follow=False, secure=False, *, headers=None, query_params=None, **extra)
Makes a PUT request on the provided ``path`` and returns a
``Response`` object. Useful for testing RESTful interfaces.
When ``data`` is provided, it is used as the request body, and
a ``Content-Type`` header is set to ``content_type``.
The ``follow``, ``secure``, ``headers``, ``query_params``, and
``extra`` parameters act the same as for :meth:`Client.get`.
.. versionchanged:: 5.1
The ``query_params`` argument was added.
.. method:: Client.patch(path, data='', content_type='application/octet-stream', follow=False, secure=False, *, headers=None, query_params=None, **extra)
Makes a PATCH request on the provided ``path`` and returns a
``Response`` object. Useful for testing RESTful interfaces.
The ``follow``, ``secure``, ``headers``, ``query_params``, and
``extra`` parameters act the same as for :meth:`Client.get`.
.. versionchanged:: 5.1
The ``query_params`` argument was added.
.. method:: Client.delete(path, data='', content_type='application/octet-stream', follow=False, secure=False, *, headers=None, query_params=None, **extra)
Makes a DELETE request on the provided ``path`` and returns a
``Response`` object. Useful for testing RESTful interfaces.
When ``data`` is provided, it is used as the request body, and
a ``Content-Type`` header is set to ``content_type``.
The ``follow``, ``secure``, ``headers``, ``query_params``, and
``extra`` parameters act the same as for :meth:`Client.get`.
.. versionchanged:: 5.1
The ``query_params`` argument was added.
.. method:: Client.trace(path, follow=False, secure=False, *, headers=None, query_params=None, **extra)
Makes a TRACE request on the provided ``path`` and returns a
``Response`` object. Useful for simulating diagnostic probes.
Unlike the other request methods, ``data`` is not provided as a keyword
parameter in order to comply with :rfc:`9110#section-9.3.8`, which
mandates that TRACE requests must not have a body.
The ``follow``, ``secure``, ``headers``, ``query_params``, and
``extra`` parameters act the same as for :meth:`Client.get`.
.. versionchanged:: 5.1
The ``query_params`` argument was added.
.. method:: Client.login(**credentials)
.. method:: Client.alogin(**credentials)
*Asynchronous version*: ``alogin()``
If your site uses Django's :doc:`authentication system</topics/auth/index>`
and you deal with logging in users, you can use the test client's
``login()`` method to simulate the effect of a user logging into the
site.
After you call this method, the test client will have all the cookies
and session data required to pass any login-based tests that may form
part of a view.
The format of the ``credentials`` argument depends on which
:ref:`authentication backend <authentication-backends>` you're using
(which is configured by your :setting:`AUTHENTICATION_BACKENDS`
setting). If you're using the standard authentication backend provided
by Django (``ModelBackend``), ``credentials`` should be the user's
username and password, provided as keyword arguments:
.. code-block:: pycon
>>> c = Client()
>>> c.login(username="fred", password="secret")
# Now you can access a view that's only available to logged-in users.
If you're using a different authentication backend, this method may
require different credentials. It requires whichever credentials are
required by your backend's ``authenticate()`` method.
``login()`` returns ``True`` if it the credentials were accepted and
login was successful.
Finally, you'll need to remember to create user accounts before you can
use this method. As we explained above, the test runner is executed
using a test database, which contains no users by default. As a result,
user accounts that are valid on your production site will not work
under test conditions. You'll need to create users as part of the test
suite -- either manually (using the Django model API) or with a test
fixture. Remember that if you want your test user to have a password,
you can't set the user's password by setting the password attribute
directly -- you must use the
:meth:`~django.contrib.auth.models.User.set_password()` function to
store a correctly hashed password. Alternatively, you can use the
:meth:`~django.contrib.auth.models.UserManager.create_user` helper
method to create a new user with a correctly hashed password.
.. versionchanged:: 5.0
``alogin()`` method was added.
.. method:: Client.force_login(user, backend=None)
.. method:: Client.aforce_login(user, backend=None)
*Asynchronous version*: ``aforce_login()``
If your site uses Django's :doc:`authentication
system</topics/auth/index>`, you can use the ``force_login()`` method
to simulate the effect of a user logging into the site. Use this method
instead of :meth:`login` when a test requires a user be logged in and
the details of how a user logged in aren't important.
Unlike ``login()``, this method skips the authentication and
verification steps: inactive users (:attr:`is_active=False
<django.contrib.auth.models.User.is_active>`) are permitted to login
and the user's credentials don't need to be provided.
The user will have its ``backend`` attribute set to the value of the
``backend`` argument (which should be a dotted Python path string), or
to ``settings.AUTHENTICATION_BACKENDS[0]`` if a value isn't provided.
The :func:`~django.contrib.auth.authenticate` function called by
:meth:`login` normally annotates the user like this.
This method is faster than ``login()`` since the expensive
password hashing algorithms are bypassed. Also, you can speed up
``login()`` by :ref:`using a weaker hasher while testing
<speeding-up-tests-auth-hashers>`.
.. versionchanged:: 5.0
``aforce_login()`` method was added.
.. method:: Client.logout()
.. method:: Client.alogout()
*Asynchronous version*: ``alogout()``
If your site uses Django's :doc:`authentication system</topics/auth/index>`,
the ``logout()`` method can be used to simulate the effect of a user
logging out of your site.
After you call this method, the test client will have all the cookies
and session data cleared to defaults. Subsequent requests will appear
to come from an :class:`~django.contrib.auth.models.AnonymousUser`.
.. versionchanged:: 5.0
``alogout()`` method was added.
Testing responses
-----------------
The ``get()`` and ``post()`` methods both return a ``Response`` object. This
``Response`` object is *not* the same as the ``HttpResponse`` object returned
by Django views; the test response object has some additional data useful for
test code to verify.
Specifically, a ``Response`` object has the following attributes:
.. class:: Response()
.. attribute:: client
The test client that was used to make the request that resulted in the
response.
.. attribute:: content
The body of the response, as a bytestring. This is the final page
content as rendered by the view, or any error message.
.. attribute:: context
The template ``Context`` instance that was used to render the template that
produced the response content.
If the rendered page used multiple templates, then ``context`` will be a
list of ``Context`` objects, in the order in which they were rendered.
Regardless of the number of templates used during rendering, you can
retrieve context values using the ``[]`` operator. For example, the
context variable ``name`` could be retrieved using:
.. code-block:: pycon
>>> response = client.get("/foo/")
>>> response.context["name"]
'Arthur'
.. admonition:: Not using Django templates?
This attribute is only populated when using the
:class:`~django.template.backends.django.DjangoTemplates` backend.
If you're using another template engine,
:attr:`~django.template.response.SimpleTemplateResponse.context_data`
may be a suitable alternative on responses with that attribute.
.. attribute:: exc_info
A tuple of three values that provides information about the unhandled
exception, if any, that occurred during the view.
The values are (type, value, traceback), the same as returned by
Python's :func:`sys.exc_info`. Their meanings are:
- *type*: The type of the exception.
- *value*: The exception instance.
- *traceback*: A traceback object which encapsulates the call stack at
the point where the exception originally occurred.
If no exception occurred, then ``exc_info`` will be ``None``.
.. method:: json(**kwargs)
The body of the response, parsed as JSON. Extra keyword arguments are
passed to :func:`json.loads`. For example:
.. code-block:: pycon
>>> response = client.get("/foo/")
>>> response.json()["name"]
'Arthur'
If the ``Content-Type`` header is not ``"application/json"``, then a
:exc:`ValueError` will be raised when trying to parse the response.
.. attribute:: request
The request data that stimulated the response.
.. attribute:: wsgi_request
The ``WSGIRequest`` instance generated by the test handler that
generated the response.
.. attribute:: status_code
The HTTP status of the response, as an integer. For a full list
of defined codes, see the `IANA status code registry`_.
.. _IANA status code registry: https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
.. attribute:: templates
A list of ``Template`` instances used to render the final content, in
the order they were rendered. For each template in the list, use
``template.name`` to get the template's file name, if the template was
loaded from a file. (The name is a string such as
``'admin/index.html'``.)
.. admonition:: Not using Django templates?
This attribute is only populated when using the
:class:`~django.template.backends.django.DjangoTemplates` backend.
If you're using another template engine,
:attr:`~django.template.response.SimpleTemplateResponse.template_name`
may be a suitable alternative if you only need the name of the
template used for rendering.
.. attribute:: resolver_match
An instance of :class:`~django.urls.ResolverMatch` for the response.
You can use the :attr:`~django.urls.ResolverMatch.func` attribute, for
example, to verify the view that served the response::
# my_view here is a function based view.
self.assertEqual(response.resolver_match.func, my_view)
# Class-based views need to compare the view_class, as the
# functions generated by as_view() won't be equal.
self.assertIs(response.resolver_match.func.view_class, MyView)
If the given URL is not found, accessing this attribute will raise a
:exc:`~django.urls.Resolver404` exception.
As with a normal response, you can also access the headers through
:attr:`.HttpResponse.headers`. For example, you could determine the content
type of a response using ``response.headers['Content-Type']``.
Exceptions
----------
If you point the test client at a view that raises an exception and
``Client.raise_request_exception`` is ``True``, that exception will be visible
in the test case. You can then use a standard ``try ... except`` block or
:meth:`~unittest.TestCase.assertRaises` to test for exceptions.
The only exceptions that are not visible to the test client are
:class:`~django.http.Http404`,
:class:`~django.core.exceptions.PermissionDenied`, :exc:`SystemExit`, and
:class:`~django.core.exceptions.SuspiciousOperation`. Django catches these
exceptions internally and converts them into the appropriate HTTP response
codes. In these cases, you can check ``response.status_code`` in your test.
If ``Client.raise_request_exception`` is ``False``, the test client will return a
500 response as would be returned to a browser. The response has the attribute
:attr:`~Response.exc_info` to provide information about the unhandled
exception.
Persistent state
----------------
The test client is stateful. If a response returns a cookie, then that cookie
will be stored in the test client and sent with all subsequent ``get()`` and
``post()`` requests.
Expiration policies for these cookies are not followed. If you want a cookie
to expire, either delete it manually or create a new ``Client`` instance (which
will effectively delete all cookies).
A test client has attributes that store persistent state information. You can
access these properties as part of a test condition.
.. attribute:: Client.cookies
A Python :class:`~http.cookies.SimpleCookie` object, containing the current
values of all the client cookies. See the documentation of the
:mod:`http.cookies` module for more.
.. attribute:: Client.session
A dictionary-like object containing session information. See the
:doc:`session documentation</topics/http/sessions>` for full details.
To modify the session and then save it, it must be stored in a variable
first (because a new ``SessionStore`` is created every time this property
is accessed)::
def test_something(self):
session = self.client.session
session["somekey"] = "test"
session.save()
.. method:: Client.asession()
.. versionadded:: 5.0
This is similar to the :attr:`session` attribute but it works in async
contexts.
Setting the language
--------------------
When testing applications that support internationalization and localization,
you might want to set the language for a test client request. The method for
doing so depends on whether or not the
:class:`~django.middleware.locale.LocaleMiddleware` is enabled.
If the middleware is enabled, the language can be set by creating a cookie with
a name of :setting:`LANGUAGE_COOKIE_NAME` and a value of the language code::
from django.conf import settings
def test_language_using_cookie(self):
self.client.cookies.load({settings.LANGUAGE_COOKIE_NAME: "fr"})
response = self.client.get("/")
self.assertEqual(response.content, b"Bienvenue sur mon site.")
or by including the ``Accept-Language`` HTTP header in the request::
def test_language_using_header(self):
response = self.client.get("/", headers={"accept-language": "fr"})
self.assertEqual(response.content, b"Bienvenue sur mon site.")
.. note::
When using these methods, ensure to reset the active language at the end of
each test::
def tearDown(self):
translation.activate(settings.LANGUAGE_CODE)
More details are in :ref:`how-django-discovers-language-preference`.
If the middleware isn't enabled, the active language may be set using
:func:`.translation.override`::
from django.utils import translation
def test_language_using_override(self):
with translation.override("fr"):
response = self.client.get("/")
self.assertEqual(response.content, b"Bienvenue sur mon site.")
More details are in :ref:`explicitly-setting-the-active-language`.
Example
-------
The following is a unit test using the test client::
import unittest
from django.test import Client
class SimpleTest(unittest.TestCase):
def setUp(self):
# Every test needs a client.
self.client = Client()
def test_details(self):
# Issue a GET request.
response = self.client.get("/customer/details/")
# Check that the response is 200 OK.
self.assertEqual(response.status_code, 200)
# Check that the rendered context contains 5 customers.
self.assertEqual(len(response.context["customers"]), 5)
.. seealso::
:class:`django.test.RequestFactory`
.. _django-testcase-subclasses:
Provided test case classes
==========================
Normal Python unit test classes extend a base class of
:class:`unittest.TestCase`. Django provides a few extensions of this base class:
.. _testcase_hierarchy_diagram:
.. figure:: _images/django_unittest_classes_hierarchy.*
:alt: Hierarchy of Django unit testing classes (TestCase subclasses)
:width: 508
:height: 328
Hierarchy of Django unit testing classes
You can convert a normal :class:`unittest.TestCase` to any of the subclasses:
change the base class of your test from ``unittest.TestCase`` to the subclass.
All of the standard Python unit test functionality will be available, and it
will be augmented with some useful additions as described in each section
below.
``SimpleTestCase``
------------------
.. class:: SimpleTestCase()
A subclass of :class:`unittest.TestCase` that adds this functionality:
* Some useful assertions like:
* Checking that a callable :meth:`raises a certain exception
<SimpleTestCase.assertRaisesMessage>`.
* Checking that a callable :meth:`triggers a certain warning
<SimpleTestCase.assertWarnsMessage>`.
* Testing form field :meth:`rendering and error treatment
<SimpleTestCase.assertFieldOutput>`.
* Testing :meth:`HTML responses for the presence/lack of a given fragment
<SimpleTestCase.assertContains>`.
* Verifying that a template :meth:`has/hasn't been used to generate a given
response content <SimpleTestCase.assertTemplateUsed>`.
* Verifying that two :meth:`URLs <SimpleTestCase.assertURLEqual>` are equal.
* Verifying an HTTP :meth:`redirect <SimpleTestCase.assertRedirects>` is
performed by the app.
* Robustly testing two :meth:`HTML fragments <SimpleTestCase.assertHTMLEqual>`
for equality/inequality or :meth:`containment <SimpleTestCase.assertInHTML>`.
* Robustly testing two :meth:`XML fragments <SimpleTestCase.assertXMLEqual>`
for equality/inequality.
* Robustly testing two :meth:`JSON fragments <SimpleTestCase.assertJSONEqual>`
for equality.
* The ability to run tests with :ref:`modified settings <overriding-settings>`.
* Using the :attr:`~SimpleTestCase.client` :class:`~django.test.Client`.
If your tests make any database queries, use subclasses
:class:`~django.test.TransactionTestCase` or :class:`~django.test.TestCase`.
.. attribute:: SimpleTestCase.databases
:class:`~SimpleTestCase` disallows database queries by default. This
helps to avoid executing write queries which will affect other tests
since each ``SimpleTestCase`` test isn't run in a transaction. If you
aren't concerned about this problem, you can disable this behavior by
setting the ``databases`` class attribute to ``'__all__'`` on your test
class.
.. warning::
``SimpleTestCase`` and its subclasses (e.g. ``TestCase``, ...) rely on
``setUpClass()`` and ``tearDownClass()`` to perform some class-wide
initialization (e.g. overriding settings). If you need to override those
methods, don't forget to call the ``super`` implementation::
class MyTestCase(TestCase):
@classmethod
def setUpClass(cls):
super().setUpClass()
...
@classmethod
def tearDownClass(cls):
...
super().tearDownClass()
Be sure to account for Python's behavior if an exception is raised during
``setUpClass()``. If that happens, neither the tests in the class nor
``tearDownClass()`` are run. In the case of :class:`django.test.TestCase`,
this will leak the transaction created in ``super()`` which results in
various symptoms including a segmentation fault on some platforms (reported
on macOS). If you want to intentionally raise an exception such as
:exc:`unittest.SkipTest` in ``setUpClass()``, be sure to do it before
calling ``super()`` to avoid this.
``TransactionTestCase``
-----------------------
.. class:: TransactionTestCase()
``TransactionTestCase`` inherits from :class:`~django.test.SimpleTestCase` to
add some database-specific features:
* Resetting the database to a known state at the beginning of each test to
ease testing and using the ORM.
* Database :attr:`~TransactionTestCase.fixtures`.
* Test :ref:`skipping based on database backend features <skipping-tests>`.
* The remaining specialized :meth:`assert*
<TransactionTestCase.assertQuerySetEqual>` methods.
Django's :class:`TestCase` class is a more commonly used subclass of
``TransactionTestCase`` that makes use of database transaction facilities
to speed up the process of resetting the database to a known state at the
beginning of each test. A consequence of this, however, is that some database
behaviors cannot be tested within a Django ``TestCase`` class. For instance,
you cannot test that a block of code is executing within a transaction, as is
required when using
:meth:`~django.db.models.query.QuerySet.select_for_update()`. In those cases,
you should use ``TransactionTestCase``.
``TransactionTestCase`` and ``TestCase`` are identical except for the manner
in which the database is reset to a known state and the ability for test code
to test the effects of commit and rollback:
* A ``TransactionTestCase`` resets the database after the test runs by
truncating all tables. A ``TransactionTestCase`` may call commit and rollback
and observe the effects of these calls on the database.
* A ``TestCase``, on the other hand, does not truncate tables after a test.
Instead, it encloses the test code in a database transaction that is rolled
back at the end of the test. This guarantees that the rollback at the end of
the test restores the database to its initial state.
.. warning::
``TestCase`` running on a database that does not support rollback (e.g. MySQL
with the MyISAM storage engine), and all instances of ``TransactionTestCase``,
will roll back at the end of the test by deleting all data from the test
database.
Apps :ref:`will not see their data reloaded <test-case-serialized-rollback>`;
if you need this functionality (for example, third-party apps should enable
this) you can set ``serialized_rollback = True`` inside the
``TestCase`` body.
``TestCase``
------------
.. class:: TestCase()
This is the most common class to use for writing tests in Django. It inherits
from :class:`TransactionTestCase` (and by extension :class:`SimpleTestCase`).
If your Django application doesn't use a database, use :class:`SimpleTestCase`.
The class:
* Wraps the tests within two nested :func:`~django.db.transaction.atomic`
blocks: one for the whole class and one for each test. Therefore, if you want
to test some specific database transaction behavior, use
:class:`TransactionTestCase`.
* Checks deferrable database constraints at the end of each test.
It also provides an additional method:
.. classmethod:: TestCase.setUpTestData()
The class-level ``atomic`` block described above allows the creation of
initial data at the class level, once for the whole ``TestCase``. This
technique allows for faster tests as compared to using ``setUp()``.
For example::
from django.test import TestCase
class MyTests(TestCase):
@classmethod
def setUpTestData(cls):
# Set up data for the whole TestCase
cls.foo = Foo.objects.create(bar="Test")
...