===========================
Testing Django applications
===========================
.. module:: django.test
:synopsis: Testing tools for Django applications.
Automated testing is an extremely useful bug-killing tool for the modern
Web developer. You can use a collection of tests -- a **test suite** -- to
solve, or avoid, a number of problems:
* When you're writing new code, you can use tests to validate your code
works as expected.
* When you're refactoring or modifying old code, you can use tests to
ensure your changes haven't affected your application's behavior
unexpectedly.
Testing a Web application is a complex task, because a Web application is made
of several layers of logic -- from HTTP-level request handling, to form
validation and processing, to template rendering. With Django's test-execution
framework and assorted utilities, you can simulate requests, insert test data,
inspect your application's output and generally verify your code is doing what
it should be doing.
The best part is, it's really easy.
This document is split into two primary sections. First, we explain how to
write tests with Django. Then, we explain how to run them.
Writing tests
=============
There are two primary ways to write tests with Django, corresponding to the
two test frameworks that ship in the Python standard library. The two
frameworks are:
* **Doctests** -- tests that are embedded in your functions' docstrings and
are written in a way that emulates a session of the Python interactive
interpreter. For example::
def my_func(a_list, idx):
"""
>>> a = ['larry', 'curly', 'moe']
>>> my_func(a, 0)
'larry'
>>> my_func(a, 1)
'curly'
"""
return a_list[idx]
* **Unit tests** -- tests that are expressed as methods on a Python class
that subclasses ``unittest.TestCase``. For example::
import unittest
class MyFuncTestCase(unittest.TestCase):
def testBasic(self):
a = ['larry', 'curly', 'moe']
self.assertEquals(my_func(a, 0), 'larry')
self.assertEquals(my_func(a, 1), 'curly')
You can choose the test framework you like, depending on which syntax you
prefer, or you can mix and match, using one framework for some of your code and
the other framework for other code. You can also use any *other* Python test
frameworks, as we'll explain in a bit.
Writing doctests
----------------
Doctests use Python's standard doctest_ module, which searches your docstrings
for statements that resemble a session of the Python interactive interpreter.
A full explanation of how doctest works is out of the scope of this document;
read Python's official documentation for the details.
.. admonition:: What's a **docstring**?
A good explanation of docstrings (and some guidelines for using them
effectively) can be found in :pep:`257`:
A docstring is a string literal that occurs as the first statement in
a module, function, class, or method definition. Such a docstring
becomes the ``__doc__`` special attribute of that object.
For example, this function has a docstring that describes what it does::
def add_two(num):
"Return the result of adding two to the provided number."
return num + 2
Because tests often make great documentation, putting tests directly in
your docstrings is an effective way to document *and* test your code.
For a given Django application, the test runner looks for doctests in two
places:
* The ``models.py`` file. You can define module-level doctests and/or a
doctest for individual models. It's common practice to put
application-level doctests in the module docstring and model-level
doctests in the model docstrings.
* A file called ``tests.py`` in the application directory -- i.e., the
directory that holds ``models.py``. This file is a hook for any and all
doctests you want to write that aren't necessarily related to models.
Here is an example model doctest::
# models.py
from django.db import models
class Animal(models.Model):
"""
An animal that knows how to make noise
# Create some animals
>>> lion = Animal.objects.create(name="lion", sound="roar")
>>> cat = Animal.objects.create(name="cat", sound="meow")
# Make 'em speak
>>> lion.speak()
'The lion says "roar"'
>>> cat.speak()
'The cat says "meow"'
"""
name = models.CharField(max_length=20)
sound = models.CharField(max_length=20)
def speak(self):
return 'The %s says "%s"' % (self.name, self.sound)
When you :ref:`run your tests <running-tests>`, the test runner will find this
docstring, notice that portions of it look like an interactive Python session,
and execute those lines while checking that the results match.
In the case of model tests, note that the test runner takes care of creating
its own test database. That is, any test that accesses a database -- by
creating and saving model instances, for example -- will not affect your
production database. However, the database is not refreshed between doctests,
so if your doctest requires a certain state you should consider flushing the
database or loading a fixture. (See the section on fixtures, below, for more
on this.) Note that to use this feature, the database user Django is connecting
as must have ``CREATE DATABASE`` rights.
For more details about how doctest works, see the `standard library
documentation for doctest`_.
.. _doctest: http://docs.python.org/library/doctest.html
.. _standard library documentation for doctest: doctest_
Writing unit tests
------------------
Like doctests, Django's unit tests use a standard library module: unittest_.
This module uses a different way of defining tests, taking a class-based
approach.
As with doctests, for a given Django application, the test runner looks for
unit tests in two places:
* The ``models.py`` file. The test runner looks for any subclass of
``unittest.TestCase`` in this module.
* A file called ``tests.py`` in the application directory -- i.e., the
directory that holds ``models.py``. Again, the test runner looks for any
subclass of ``unittest.TestCase`` in this module.
This example ``unittest.TestCase`` subclass is equivalent to the example given
in the doctest section above::
import unittest
from myapp.models import Animal
class AnimalTestCase(unittest.TestCase):
def setUp(self):
self.lion = Animal.objects.create(name="lion", sound="roar")
self.cat = Animal.objects.create(name="cat", sound="meow")
def testSpeaking(self):
self.assertEquals(self.lion.speak(), 'The lion says "roar"')
self.assertEquals(self.cat.speak(), 'The cat says "meow"')
When you :ref:`run your tests <running-tests>`, the default behavior of the
test utility is to find all the test cases (that is, subclasses of
``unittest.TestCase``) in ``models.py`` and ``tests.py``, automatically build a
test suite out of those test cases, and run that suite.
There is a second way to define the test suite for a module: if you define a
function called ``suite()`` in either ``models.py`` or ``tests.py``, the
Django test runner will use that function to construct the test suite for that
module. This follows the `suggested organization`_ for unit tests. See the
Python documentation for more details on how to construct a complex test
suite.
For more details about ``unittest``, see the `standard library unittest
documentation`_.
.. _unittest: http://docs.python.org/library/unittest.html
.. _standard library unittest documentation: unittest_
.. _suggested organization: http://docs.python.org/library/unittest.html#organizing-tests
Which should I use?
-------------------
Because Django supports both of the standard Python test frameworks, it's up to
you and your tastes to decide which one to use. You can even decide to use
*both*.
For developers new to testing, however, this choice can seem confusing. Here,
then, are a few key differences to help you decide which approach is right for
you:
* If you've been using Python for a while, ``doctest`` will probably feel
more "pythonic". It's designed to make writing tests as easy as possible,
so it requires no overhead of writing classes or methods. You simply put
tests in docstrings. This has the added advantage of serving as
documentation (and correct documentation, at that!).
If you're just getting started with testing, using doctests will probably
get you started faster.
* The ``unittest`` framework will probably feel very familiar to developers
coming from Java. ``unittest`` is inspired by Java's JUnit, so you'll
feel at home with this method if you've used JUnit or any test framework
inspired by JUnit.
* If you need to write a bunch of tests that share similar code, then
you'll appreciate the ``unittest`` framework's organization around
classes and methods. This makes it easy to abstract common tasks into
common methods. The framework also supports explicit setup and/or cleanup
routines, which give you a high level of control over the environment
in which your test cases are run.
Again, remember that you can use both systems side-by-side (even in the same
app). In the end, most projects will eventually end up using both. Each shines
in different circumstances.
.. _running-tests:
Running tests
=============
Once you've written tests, run them using the :djadmin:`test` command of
your project's ``manage.py`` utility::
$ ./manage.py test
By default, this will run every test in every application in
:setting:`INSTALLED_APPS`. If you only want to run tests for a particular
application, add the application name to the command line. For example, if your
:setting:`INSTALLED_APPS` contains ``'myproject.polls'`` and
``'myproject.animals'``, you can run the ``myproject.animals`` unit tests alone
with this command::
$ ./manage.py test animals
Note that we used ``animals``, not ``myproject.animals``.
.. versionadded:: 1.0
You can now choose which test to run.
You can be even *more* specific by naming an individual test case. To
run a single test case in an application (for example, the
``AnimalTestCase`` described in the "Writing unit tests" section), add
the name of the test case to the label on the command line::
$ ./manage.py test animals.AnimalTestCase
And it gets even more granular than that! To run a *single* test
method inside a test case, add the name of the test method to the
label::
$ ./manage.py test animals.AnimalTestCase.testFluffyAnimals
.. versionadded:: 1.2
The ability to select individual doctests was added.
You can use the same rules if you're using doctests. Django will use the
test label as a path to the test method or class that you want to run.
If your ``models.py`` or ``tests.py`` has a function with a doctest, or
class with a class-level doctest, you can invoke that test by appending the
name of the test method or class to the label::
$ ./manage.py test animals.classify
If you want to run the doctest for a specific method in a class, add the
name of the method to the label::
$ ./manage.py test animals.Classifier.run
If you're using a ``__test__`` dictionary to specify doctests for a
module, Django will use the label as a key in the ``__test__`` dictionary
for defined in ``models.py`` and ``tests.py``.
.. versionadded:: 1.2
You can now trigger a graceful exit from a test run by pressing ``Ctrl-C``.
If you press ``Ctrl-C`` while the tests are running, the test runner will
wait for the currently running test to complete and then exit gracefully.
During a graceful exit the test runner will output details of any test
failures, report on how many tests were run and how many errors and failures
were encountered, and destroy any test databases as usual. Thus pressing
``Ctrl-C`` can be very useful if you forget to pass the :djadminopt:`--failfast`
option, notice that some tests are unexpectedly failing, and want to get details
on the failures without waiting for the full test run to complete.
If you do not want to wait for the currently running test to finish, you
can press ``Ctrl-C`` a second time and the test run will halt immediately,
but not gracefully. No details of the tests run before the interruption will
be reported, and any test databases created by the run will not be destroyed.
.. admonition:: Test with warnings enabled
It is a good idea to run your tests with ``python -Wall manage.py
test``. This will allow you to catch any deprecation warnings that
might be in your code. Django (as well as many other libraries) use
warnings to flag when features are deprecated. It can also flag
areas in your code that are not strictly wrong, but may benefit
from a better implementation.
Running tests outside the test runner
-------------------------------------
If you want to run tests outside of ``./manage.py test`` -- for example,
from a shell prompt -- you will need to set up the test
environment first. Django provides a convenience method to do this::
>>> from django.test.utils import setup_test_environment
>>> setup_test_environment()
This convenience method sets up the test database, and puts other
Django features into modes that allow for repeatable testing.
The call to :meth:`~django.test.utils.setup_test_environment` is made
automatically as part of the setup of `./manage.py test`. You only
need to manually invoke this method if you're not using running your
tests via Django's test runner.
The test database
-----------------
Tests that require a database (namely, model tests) will not use your "real"
(production) database. Separate, blank databases are created for the tests.
Regardless of whether the tests pass or fail, the test databases are destroyed
when all the tests have been executed.
By default the test databases get their names by prepending ``test_``
to the value of the :setting:`NAME` settings for the databases
defined in :setting:`DATABASES`. When using the SQLite database engine
the tests will by default use an in-memory database (i.e., the
database will be created in memory, bypassing the filesystem
entirely!). If you want to use a different database name, specify
:setting:`TEST_NAME` in the dictionary for any given database in
:setting:`DATABASES`.
Aside from using a separate database, the test runner will otherwise
use all of the same database settings you have in your settings file:
:setting:`ENGINE`, :setting:`USER`, :setting:`HOST`, etc. The test
database is created by the user specified by ``USER``, so you'll need
to make sure that the given user account has sufficient privileges to
create a new database on the system.
.. versionadded:: 1.0
For fine-grained control over the character encoding of your test
database, use the :setting:`TEST_CHARSET` option. If you're using
MySQL, you can also use the :setting:`TEST_COLLATION` option to
control the particular collation used by the test database. See the
:doc:`settings documentation </ref/settings>` for details of these
advanced settings.
.. _topics-testing-masterslave:
Testing master/slave configurations
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. versionadded:: 1.2
If you're testing a multiple database configuration with master/slave
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 master won't be seen on the
slave.
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': 'dbmaster',
# ... plus some other settings
},
'slave': {
'ENGINE': 'django.db.backends.mysql',
'NAME': 'myproject',
'HOST': 'dbslave',
'TEST_MIRROR': 'default'
# ... plus some other settings
}
}
In this setup, we have two database servers: ``dbmaster``, described
by the database alias ``default``, and ``dbslave`` described by the
alias ``slave``. As you might expect, ``dbslave`` has been configured
by the database administrator as a read slave of ``dbmaster``, so in
normal activity, any write to ``default`` will appear on ``slave``.
If Django created two independent test databases, this would break any
tests that expected replication to occur. However, the ``slave``
database has been configured as a test mirror (using the
:setting:`TEST_MIRROR` setting), indicating that under testing,
``slave`` should be treated as a mirror of ``default``.
When the test environment is configured, a test version of ``slave``
will *not* be created. Instead the connection to ``slave``
will be redirected to point at ``default``. As a result, writes to
``default`` will appear on ``slave`` -- but because they are actually
the same database, not because there is data replication between the
two databases.
.. _topics-testing-creation-dependencies:
Controlling creation order for test databases
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. versionadded:: 1.2.4
By default, Django will 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
:setting:`TEST_DEPENDENCIES` setting. Consider the following
(simplified) example database configuration::
DATABASES = {
'default': {
# ... db settings
'TEST_DEPENDENCIES': ['diamonds']
},
'diamonds': {
# ... db settings
},
'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
:setting:`TEST_DEPENDENCIES` definition, an ``ImproperlyConfigured``
exception will be raised.
Other test conditions
---------------------
Regardless of the value of the :setting:`DEBUG` setting in your configuration
file, all Django tests run with :setting:`DEBUG`\=False. This is to ensure that
the observed output of your code matches what will be seen in a production
setting.
Understanding the test output
-----------------------------
When you run your tests, you'll see a number of messages as the test runner
prepares itself. You can control the level of detail of these messages with the
``verbosity`` option on the command line::
Creating test database...
Creating table myapp_animal
Creating table myapp_mineral
Loading 'initial_data' fixtures...
No fixtures found.
This tells you that the test runner is creating a test database, as described
in the previous section.
Once the test database has been created, Django will run your tests.
If everything goes well, you'll see something like this::
----------------------------------------------------------------------
Ran 22 tests in 0.221s
OK
If there are test failures, however, you'll see full details about which tests
failed::
======================================================================
FAIL: Doctest: ellington.core.throttle.models
----------------------------------------------------------------------
Traceback (most recent call last):
File "/dev/django/test/doctest.py", line 2153, in runTest
raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: Failed doctest test for myapp.models
File "/dev/myapp/models.py", line 0, in models
----------------------------------------------------------------------
File "/dev/myapp/models.py", line 14, in myapp.models
Failed example:
throttle.check("actor A", "action one", limit=2, hours=1)
Expected:
True
Got:
False
----------------------------------------------------------------------
Ran 2 tests in 0.048s
FAILED (failures=1)
A full explanation of this error output is beyond the scope of this document,
but it's pretty intuitive. You can consult the documentation of Python's
``unittest`` library for details.
Note that the return code for the test-runner script is the total number of
failed and erroneous tests. If all the tests pass, the return code is 0. This
feature is useful if you're using the test-runner script in a shell script and
need to test for success or failure at that level.
Testing tools
=============
Django provides a small set of tools that come in handy when writing tests.
The test client
---------------
.. module:: django.test.client
:synopsis: Django's 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.
* Test that the correct view is executed for a given URL.
* 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 Twill_,
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 view is being
called and that the view is collecting the correct context data.
* Use in-browser frameworks such as Twill and Selenium to test *rendered*
HTML and the *behavior* of Web pages, namely JavaScript functionality.
A comprehensive test suite should use a combination of both test types.
.. _Twill: http://twill.idyll.org/
.. _Selenium: http://seleniumhq.org/
Overview and a quick example
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To use the test client, instantiate ``django.test.client.Client`` and retrieve
Web pages::
>>> from django.test.client import Client
>>> c = Client()
>>> response = c.post('/login/', {'username': 'john', 'password': 'smith'})
>>> response.status_code
200
>>> response = c.get('/customer/details/')
>>> response.content
'<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 ...'
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::
>>> c.get('/login/')
This is incorrect::
>>> c.get('http://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 urllib_ or urllib2_.
* 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.
.. versionadded:: 1.2.2
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::
>>> from django.test import Client
>>> csrf_client = Client(enforce_csrf_checks=True)
.. _urllib: http://docs.python.org/library/urllib.html
.. _urllib2: http://docs.python.org/library/urllib2.html
Making requests
~~~~~~~~~~~~~~~
Use the ``django.test.client.Client`` class to make requests. It requires no
arguments at time of construction:
.. class:: Client()
Once you have a ``Client`` instance, you can call any of the following
methods:
.. method:: Client.get(path, data={}, follow=False, **extra)
Makes a GET 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 create a GET
data payload. For example::
>>> c = Client()
>>> c.get('/customers/details/', {'name': 'fred', 'age': 7})
...will result in the evaluation of a GET request equivalent to::
/customers/details/?name=fred&age=7
The ``extra`` keyword arguments parameter can be used to specify
headers to be sent in the request. For example::
>>> c = Client()
>>> c.get('/customers/details/', {'name': 'fred', 'age': 7},
... HTTP_X_REQUESTED_WITH='XMLHttpRequest')
...will send the HTTP header ``HTTP_X_REQUESTED_WITH`` to the
details view, which is a good way to test code paths that use the
:meth:`django.http.HttpRequest.is_ajax()` method.
.. versionadded:: 1.1
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::
>>> c = Client()
>>> c.get('/customers/details/?name=fred&age=7')
If you provide a URL with both an encoded GET data and a data argument,
the data argument 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 an url ``/redirect_me/`` that redirected to ``/next/``, that
redirected to ``/final/``, this is what you'd see::
>>> response = c.get('/redirect_me/', follow=True)
>>> response.redirect_chain
[(u'http://testserver/next/', 302), (u'http://testserver/final/', 302)]
.. method:: Client.post(path, data={}, content_type=MULTIPART_CONTENT, follow=False, **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::
>>> c = Client()
>>> c.post('/login/', {'name': 'fred', 'passwd': 'secret'})
...will result in the evaluation of a POST request to this URL::
/login/
...with this POST data::
name=fred&passwd=secret
If you provide ``content_type`` (e.g., ``text/xml`` for an XML
payload), the contents of ``data`` will be 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
``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::
>>> c = Client()
>>> f = open('wishlist.doc')
>>> c.post('/customers/wishes/', {'name': 'fred', 'attachment': f})
>>> f.close()
(The name ``attachment`` here is not relevant; use whatever name your
file-processing code expects.)
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 ``extra`` argument acts the same as for :meth:`Client.get`.
.. versionchanged:: 1.1
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::
>>> c.post('/login/?visitor=true', {'name': 'fred', 'passwd': 'secret'})
... 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.
.. method:: Client.head(path, data={}, follow=False, **extra)
.. versionadded:: 1.1
Makes a HEAD request on the provided ``path`` and returns a ``Response``
object. Useful for testing RESTful interfaces. Acts just like
:meth:`Client.get` except it does not return a message body.
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.
.. method:: Client.options(path, data={}, follow=False, **extra)
.. versionadded:: 1.1
Makes an OPTIONS request on the provided ``path`` and returns a
``Response`` object. Useful for testing RESTful interfaces.
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.
The ``extra`` argument acts the same as for :meth:`Client.get`.
.. method:: Client.put(path, data={}, content_type=MULTIPART_CONTENT, follow=False, **extra)
.. versionadded:: 1.1
Makes a PUT request on the provided ``path`` and returns a
``Response`` object. Useful for testing RESTful interfaces. Acts just
like :meth:`Client.post` except with the PUT request method.
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.
.. method:: Client.delete(path, follow=False, **extra)
.. versionadded:: 1.1
Makes an DELETE request on the provided ``path`` and returns a
``Response`` object. Useful for testing RESTful interfaces.
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.
The ``extra`` argument acts the same as for :meth:`Client.get`.
.. method:: Client.login(**credentials)
.. versionadded:: 1.0
If your site uses Django's :doc:`authentication system</topics/auth>`
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::
>>> 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.
.. method:: Client.logout()
.. versionadded:: 1.0
If your site uses Django's :doc:`authentication system</topics/auth>`,
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 AnonymousUser.
Testing responses
~~~~~~~~~~~~~~~~~
The ``get()`` and ``post()`` methods both return a ``Response`` object. This
``Response`` object is *not* the same as the ``HttpResponse`` object returned
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 string. 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.
.. versionadded:: 1.1
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::
>>> response = client.get('/foo/')
>>> response.context['name']
'Arthur'
.. attribute:: request
The request data that stimulated the response.
.. attribute:: status_code
The HTTP status of the response, as an integer. See RFC2616_ for a full
list of HTTP status codes.
.. attribute:: template
The ``Template`` instance that was used to render the final content. 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'``.)
If the rendered page used multiple templates -- e.g., using :ref:`template
inheritance<template-inheritance>` -- then ``template`` will be a list of
``Template`` instances, in the order in which they were rendered.
You can also use dictionary syntax on the response object to query the value
of any settings in the HTTP headers. For example, you could determine the
content type of a response using ``response['Content-Type']``.
.. _RFC2616: http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html
Exceptions
~~~~~~~~~~
If you point the test client at a view that raises an exception, that exception
will be visible in the test case. You can then use a standard ``try...except``
block or ``unittest.TestCase.assertRaises()`` to test for exceptions.
The only exceptions that are not visible to the test client are ``Http404``,
``PermissionDenied`` and ``SystemExit``. 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.
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 two attributes that store persistent state information. You
can access these properties as part of a test condition.
.. attribute:: Client.cookies
A Python ``SimpleCookie`` object, containing the current values of all the
client cookies. See the `Cookie module documentation`_ 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()
.. _Cookie module documentation: http://docs.python.org/library/cookie.html
Example
~~~~~~~
The following is a simple unit test using the test client::
import unittest
from django.test.client 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.failUnlessEqual(response.status_code, 200)
# Check that the rendered context contains 5 customers.
self.failUnlessEqual(len(response.context['customers']), 5)
TestCase
--------
.. currentmodule:: django.test
Normal Python unit test classes extend a base class of ``unittest.TestCase``.
Django provides an extension of this base class:
.. class:: TestCase()
This class provides some additional capabilities that can be useful for testing
Web sites.
Converting a normal ``unittest.TestCase`` to a Django ``TestCase`` is easy:
just change the base class of your test from ``unittest.TestCase`` to
``django.test.TestCase``. All of the standard Python unit test functionality
will continue to be available, but it will be augmented with some useful
additions.
.. versionadded:: 1.1
.. class:: TransactionTestCase()
Django ``TestCase`` classes make use of database transaction facilities, if
available, 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 the
effects of transaction commit and rollback cannot be tested by a Django
``TestCase`` class. If your test requires testing of such transactional
behavior, you should use a Django ``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 before the test runs by truncating all tables and reloading
initial data. 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 and reload initial
data at the beginning of a test. Instead, it encloses the test code in a
database transaction that is rolled back at the end of the test. It also
prevents the code under test from issuing any commit or rollback operations
on the database, to ensure that the rollback at the end of the test restores
the database to its initial state. In order to guarantee that all ``TestCase``
code starts with a clean database, the Django test runner runs all ``TestCase``
tests first, before any other tests (e.g. doctests) that may alter the
database without restoring it to its original state.
When running on a database that does not support rollback (e.g. MySQL with the
MyISAM storage engine), ``TestCase`` falls back to initializing the database
by truncating tables and reloading initial data.
.. note::
The ``TestCase`` use of rollback to un-do the effects of the test code
may reveal previously-undetected errors in test code. For example,
test code that assumes primary keys values will be assigned starting at
one may find that assumption no longer holds true when rollbacks instead
of table truncation are being used to reset the database. Similarly,
the reordering of tests so that all ``TestCase`` classes run first may
reveal unexpected dependencies on test case ordering. In such cases a
quick fix is to switch the ``TestCase`` to a ``TransactionTestCase``.
A better long-term fix, that allows the test to take advantage of the
speed benefit of ``TestCase``, is to fix the underlying test problem.
Default test client
~~~~~~~~~~~~~~~~~~~
.. versionadded:: 1.0
.. attribute:: TestCase.client
Every test case in a ``django.test.TestCase`` instance has access to an
instance of a Django test client. This client can be accessed as
``self.client``. This client is recreated for each test, so you don't have to
worry about state (such as cookies) carrying over from one test to another.
This means, instead of instantiating a ``Client`` in each test::
import unittest
from django.test.client import Client
class SimpleTest(unittest.TestCase):
def test_details(self):
client = Client()
response = client.get('/customer/details/')
self.failUnlessEqual(response.status_code, 200)
def test_index(self):
client = Client()
response = client.get('/customer/index/')
self.failUnlessEqual(response.status_code, 200)
...you can just refer to ``self.client``, like so::
from django.test import TestCase
class SimpleTest(TestCase):
def test_details(self):
response = self.client.get('/customer/details/')
self.failUnlessEqual(response.status_code, 200)
def test_index(self):
response = self.client.get('/customer/index/')
self.failUnlessEqual(response.status_code, 200)
.. _topics-testing-fixtures:
Fixture loading
~~~~~~~~~~~~~~~
.. attribute:: TestCase.fixtures
A test case for a database-backed Web site isn't much use if there isn't any
data in the database. To make it easy to put test data into the database,
Django's custom ``TestCase`` class provides a way of loading **fixtures**.
A fixture is a collection of data that Django knows how to import into a
database. For example, if your site has user accounts, you might set up a
fixture of fake user accounts in order to populate your database during tests.
The most straightforward way of creating a fixture is to use the
:djadmin:`manage.py dumpdata <dumpdata>` command. This assumes you
already have some data in your database. See the :djadmin:`dumpdata
documentation<dumpdata>` for more details.
.. note::
If you've ever run :djadmin:`manage.py syncdb<syncdb>`, you've
already used a fixture without even knowing it! When you call
:djadmin:`syncdb` in the database for the first time, Django
installs a fixture called ``initial_data``. This gives you a way
of populating a new database with any initial data, such as a
default set of categories.
Fixtures with other names can always be installed manually using
the :djadmin:`manage.py loaddata<loaddata>` command.
Once you've created a fixture and placed it in a ``fixtures`` directory in one
of your :setting:`INSTALLED_APPS`, you can use it in your unit tests by
specifying a ``fixtures`` class attribute on your :class:`django.test.TestCase`
subclass::
from django.test import TestCase
from myapp.models import Animal
class AnimalTestCase(TestCase):
fixtures = ['mammals.json', 'birds']
def setUp(self):
# Test definitions as before.
call_setup_methods()
def testFluffyAnimals(self):
# A test that uses the fixtures.
call_some_test_code()
Here's specifically what will happen:
* At the start of each test case, before ``setUp()`` is run, Django will
flush the database, returning the database to the state it was in
directly after :djadmin:`syncdb` was called.
* Then, all the named fixtures are installed. In this example, Django will
install any JSON fixture named ``mammals``, followed by any fixture named
``birds``. See the :djadmin:`loaddata` documentation for more
details on defining and installing fixtures.
This flush/load procedure is repeated for each test in the test case, so you
can be certain that the outcome of a test will not be affected by another test,
or by the order of test execution.
URLconf configuration
~~~~~~~~~~~~~~~~~~~~~
.. versionadded:: 1.0
.. attribute:: TestCase.urls
If your application provides views, you may want to include tests that use the
test client to exercise those views. However, an end user is free to deploy the
views in your application at any URL of their choosing. This means that your
tests can't rely upon the fact that your views will be available at a
particular URL.
In order to provide a reliable URL space for your test,
``django.test.TestCase`` provides the ability to customize the URLconf
configuration for the duration of the execution of a test suite. If your
``TestCase`` instance defines an ``urls`` attribute, the ``TestCase`` will use
the value of that attribute as the ``ROOT_URLCONF`` for the duration of that
test.
For example::
from django.test import TestCase
class TestMyViews(TestCase):
urls = 'myapp.test_urls'
def testIndexPageView(self):
# Here you'd test your view using ``Client``.
call_some_test_code()
This test case will use the contents of ``myapp.test_urls`` as the
URLconf for the duration of the test case.
.. _emptying-test-outbox:
Multi-database support
~~~~~~~~~~~~~~~~~~~~~~
.. attribute:: TestCase.multi_db
.. versionadded:: 1.2
Django sets up a test database corresponding to every database that is
defined in the :setting:`DATABASES` definition in your settings
file. However, a big part of the time taken to run a Django TestCase
is consumed by the call to ``flush`` that ensures that you have a
clean database at the start of each test run. If you have multiple
databases, multiple flushes are required (one for each database),
which can be a time consuming activity -- especially if your tests
don't need to test multi-database activity.
As an optimization, Django only flushes the ``default`` database at
the start of each test run. If your setup contains multiple databases,
and you have a test that requires every database to be clean, you can
use the ``multi_db`` attribute on the test suite to request a full
flush.
For example::
class TestMyViews(TestCase):
multi_db = True
def testIndexPageView(self):
call_some_test_code()
This test case will flush *all* the test databases before running
``testIndexPageView``.
Emptying the test outbox
~~~~~~~~~~~~~~~~~~~~~~~~
.. versionadded:: 1.0
If you use Django's custom ``TestCase`` class, the test runner will clear the
contents of the test e-mail outbox at the start of each test case.
For more detail on e-mail services during tests, see `E-mail services`_.
Assertions
~~~~~~~~~~
.. versionadded:: 1.0
.. versionchanged:: 1.2
Addded ``msg_prefix`` argument.
As Python's normal ``unittest.TestCase`` class implements assertion methods
such as ``assertTrue`` and ``assertEquals``, Django's custom ``TestCase`` class
provides a number of custom assertion methods that are useful for testing Web
applications:
The failure messages given by the assertion methods can be customized
with the ``msg_prefix`` argument. This string will be prefixed to any
failure message generated by the assertion. This allows you to provide
additional details that may help you to identify the location and
cause of an failure in your test suite.
.. method:: TestCase.assertContains(response, text, count=None, status_code=200, msg_prefix='')
Asserts that a ``Response`` instance produced the given ``status_code`` and
that ``text`` appears in the content of the response. If ``count`` is
provided, ``text`` must occur exactly ``count`` times in the response.
.. method:: TestCase.assertNotContains(response, text, status_code=200, msg_prefix='')
Asserts that a ``Response`` instance produced the given ``status_code`` and
that ``text`` does not appears in the content of the response.
.. method:: TestCase.assertFormError(response, form, field, errors, msg_prefix='')
Asserts that a field on a form raises the provided list of errors when
rendered on the form.
``form`` is the name the ``Form`` instance was given in the template
context.
``field`` is the name of the field on the form to check. If ``field``
has a value of ``None``, non-field errors (errors you can access via
``form.non_field_errors()``) will be checked.
``errors`` is an error string, or a list of error strings, that are
expected as a result of form validation.
.. method:: TestCase.assertTemplateUsed(response, template_name, msg_prefix='')
Asserts that the template with the given name was used in rendering the
response.
The name is a string such as ``'admin/index.html'``.
.. method:: TestCase.assertTemplateNotUsed(response, template_name, msg_prefix='')
Asserts that the template with the given name was *not* used in rendering
the response.
.. method:: TestCase.assertRedirects(response, expected_url, status_code=302, target_status_code=200, msg_prefix='')
Asserts that the response return a ``status_code`` redirect status, it
redirected to ``expected_url`` (including any GET data), and the final
page was received with ``target_status_code``.
.. versionadded:: 1.1
If your request used the ``follow`` argument, the ``expected_url`` and
``target_status_code`` will be the url and status code for the final
point of the redirect chain.
.. _topics-testing-email:
E-mail services
---------------
.. versionadded:: 1.0
If any of your Django views send e-mail using :doc:`Django's e-mail
functionality </topics/email>`, you probably don't want to send e-mail each time
you run a test using that view. For this reason, Django's test runner
automatically redirects all Django-sent e-mail to a dummy outbox. This lets you
test every aspect of sending e-mail -- from the number of messages sent to the
contents of each message -- without actually sending the messages.
The test runner accomplishes this by transparently replacing the normal
email backend with a testing backend.
(Don't worry -- this has no effect on any other e-mail senders outside of
Django, such as your machine's mail server, if you're running one.)
.. currentmodule:: django.core.mail
.. data:: django.core.mail.outbox
During test running, each outgoing e-mail is saved in
``django.core.mail.outbox``. This is a simple list of all
:class:`~django.core.mail.EmailMessage` instances that have been sent.
The ``outbox`` attribute is a special attribute that is created *only* when
the ``locmem`` e-mail backend is used. It doesn't normally exist as part of the
:mod:`django.core.mail` module and you can't import it directly. The code
below shows how to access this attribute correctly.
Here's an example test that examines ``django.core.mail.outbox`` for length
and contents::
from django.core import mail
from django.test import TestCase
class EmailTest(TestCase):
def test_send_email(self):
# Send message.
mail.send_mail('Subject here', 'Here is the message.',
'from@example.com', ['to@example.com'],
fail_silently=False)
# Test that one message has been sent.
self.assertEquals(len(mail.outbox), 1)
# Verify that the subject of the first message is correct.
self.assertEquals(mail.outbox[0].subject, 'Subject here')
As noted :ref:`previously <emptying-test-outbox>`, the test outbox is emptied
at the start of every test in a Django ``TestCase``. To empty the outbox
manually, assign the empty list to ``mail.outbox``::
from django.core import mail
# Empty the test outbox
mail.outbox = []
Using different testing frameworks
==================================
Clearly, ``doctest`` and ``unittest`` are not the only Python testing
frameworks. 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 :setting:`TEST_RUNNER`
setting to determine what to do. By default, :setting:`TEST_RUNNER` points to
``'django.test.simple.DjangoTestSuiteRunner'``. This class defines the default Django
testing behavior. This behavior involves:
#. Performing global pre-test setup.
#. Looking for unit tests and doctests in the ``models.py`` and
``tests.py`` files in each installed application.
#. Creating the test databases.
#. Running ``syncdb`` to install models and initial data into the test
databases.
#. Running the unit tests and doctests that are found.
#. Destroying the test databases.
#. Performing global post-test teardown.
If you define your own test runner class and point :setting:`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.
.. _topics-testing-test_runner:
Defining a test runner
----------------------
.. versionchanged:: 1.2
Prior to 1.2, test runners were a single function, not a class.
.. currentmodule:: django.test.simple
A test runner is a class defining a ``run_tests()`` method. Django ships
with a ``DjangoTestSuiteRunner`` 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 to by ``run_tests()`` to
set up, execute and tear down the test suite.
.. class:: DjangoTestSuiteRunner(verbosity=1, interactive=True, failfast=True, **kwargs)
``verbosity`` determines the amount of notification and debug information
that will be printed to the console; ``0`` is no output, ``1`` is normal
output, and ``2`` is verbose output.
If ``interactive`` is ``True``, 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. If ``interactive`` is ``False``, the test suite must be able to
run without any manual intervention.
If ``failfast`` is ``True``, the test suite will stop running after the
first test failure is detected.
Django will, from time to time, extend the capabilities of
the test runner by adding new arguments. The ``**kwargs`` declaration
allows for this expansion. If you subclass ``DjangoTestSuiteRunner`` or
write your own test runner, ensure accept and handle the ``**kwargs``
parameter.
.. method:: DjangoTestSuiteRunner.run_tests(test_labels, extra_tests=None, **kwargs)
Run the test suite.
``test_labels`` is a list of strings describing the tests to be run. A test
label can take one of three forms:
* ``app.TestCase.test_method`` -- Run a single test method in a test
case.
* ``app.TestCase`` -- Run all the test methods in a test case.
* ``app`` -- Search for and run all tests in the named application.
If ``test_labels`` has a value of ``None``, the test runner should run
search for tests in all the applications in :setting:`INSTALLED_APPS`.
``extra_tests`` is a list of extra ``TestCase`` 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 in ``test_labels``.
This method should return the number of tests that failed.
.. method:: DjangoTestSuiteRunner.setup_test_environment(**kwargs)
Sets up the test environment ready for testing.
.. method:: DjangoTestSuiteRunner.build_suite(test_labels, extra_tests=None, **kwargs)
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 three forms:
* ``app.TestCase.test_method`` -- Run a single test method in a test
case.
* ``app.TestCase`` -- Run all the test methods in a test case.
* ``app`` -- Search for and run all tests in the named application.
If ``test_labels`` has a value of ``None``, the test runner should run
search for tests in all the applications in :setting:`INSTALLED_APPS`.
``extra_tests`` is a list of extra ``TestCase`` 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 in ``test_labels``.
Returns a ``TestSuite`` instance ready to be run.
.. method:: DjangoTestSuiteRunner.setup_databases(**kwargs)
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.
.. method:: DjangoTestSuiteRunner.run_suite(suite, **kwargs)
Runs the test suite.
Returns the result produced by the running the test suite.
.. method:: DjangoTestSuiteRunner.teardown_databases(old_config, **kwargs)
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 is the return
value of the ``setup_databases()`` method.
.. method:: DjangoTestSuiteRunner.teardown_test_environment(**kwargs)
Restores the pre-test environment.
.. method:: DjangoTestSuiteRunner.suite_result(suite, result, **kwargs)
Computes and returns a return code based on a test suite, and the result
from that test suite.
Testing utilities
-----------------
.. module:: django.test.utils
:synopsis: Helpers to write custom test runners.
To assist in the creation of your own test runner, Django provides a number of
utility methods in the ``django.test.utils`` module.
.. function:: setup_test_environment()
Performs any global pre-test setup, such as the installing the
instrumentation of the template rendering system and setting up
the dummy ``SMTPConnection``.
.. function:: teardown_test_environment()
Performs any global post-test teardown, such as removing the black
magic hooks into the template system and restoring normal e-mail
services.
The creation module of the database backend (``connection.creation``)
also provides some utilities that can be useful during testing.
.. function:: create_test_db(verbosity=1, autoclobber=False)
Creates a new test database and runs ``syncdb`` against it.
``verbosity`` has the same behavior as in ``run_tests()``.
``autoclobber`` describes the behavior that will occur if a
database with the same name as the test database is discovered:
* If ``autoclobber`` is ``False``, 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.
Returns the name of the test database that it created.
``create_test_db()`` has the side effect of modifying the value of
:setting:`NAME` in :setting:`DATABASES` to match the name of the test
database.
.. versionchanged:: 1.0
``create_test_db()`` now returns the name of the test database.
.. function:: destroy_test_db(old_database_name, verbosity=1)
Destroys the database whose name is in stored in :setting:`NAME` in the
:setting:`DATABASES`, and sets :setting:`NAME` to use the
provided name.
``verbosity`` has the same behavior as in ``run_tests()``.