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diff --git a/docs/testing.txt b/docs/testing.txt new file mode 100644 index 0000000000..98ed1e8aec --- /dev/null +++ b/docs/testing.txt @@ -0,0 +1,303 @@ +=========================== +Testing Django applications +=========================== + +**New in Django development version**. + +Automated testing is an extremely useful weapon in the bug-killing arsenal +of the modern developer. When initially writing code, a test suite can be +used to validate that code behaves as expected. When refactoring or +modifying code, tests serve as a guide to ensure that behavior hasn't +changed unexpectedly as a result of the refactor. + +Testing an web application is a complex task, as there are many +components of a web application that must be validated and tested. To +help you test your application, Django provides a test execution +framework, and range of utilities that can be used to stimulate and +inspect various facets of a web application. + + This testing framework is currently under development, and may change + slightly before the next official Django release. + + (That's *no* excuse not to write tests, though!) + +Writing tests +============= + +Tests in Django come in two forms: doctests and unit tests. + +Writing doctests +---------------- + +Doctests use Python's standard doctest_ module, which searches for tests in +your docstrings. Django's test runner looks for doctests in your ``models.py`` +file, and executes any that it finds. Django will also search for a file +called ``tests.py`` in the application directory (i.e., the directory that +holds ``models.py``). If a ``tests.py`` is found, it will also be searched +for doctests. + +.. admonition:: What's a **docstring**? + + A good explanation of docstrings (and some guidlines 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. + + Since tests often make great documentation, doctest lets you put your + tests directly in your docstrings. + +You can put doctest strings on any object in your ``models.py``, but it's +common practice to put application-level doctests in the module docstring, and +model-level doctests in the docstring for each model. + +For example:: + + from django.db import model + + 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(maxlength=20) + sound = models.CharField(maxlength=20) + + def speak(self): + return 'The %s says "%s"' % (self.name, self.sound) + +When you `run your tests`_, the test utility 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. + +For more details about how doctest works, see the `standard library +documentation for doctest`_ + +.. _doctest: http://docs.python.org/lib/module-doctest.html +.. _standard library documentation for doctest: doctest_ + +Writing unittests +----------------- + +Like doctests, Django's unit tests use a standard library module: unittest_. +As with doctests, Django's test runner looks for any unit test cases defined +in ``models.py``, or in a ``tests.py`` file in your application directory. + +An equivalent unittest test case for the above example would look like:: + + 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 `run your tests`_, the test utility will find all the test cases +(that is, subclasses of ``unittest.TestCase``) in ``tests.py``, automatically +build a test suite out of those test cases, and run that suite. + +For more details about ``unittest``, see the `standard library unittest +documentation`_. + +.. _unittest: http://docs.python.org/lib/module-unittest.html +.. _standard library unittest documentation: unittest_ +.. _run your tests: `Running tests`_ + +Which should I use? +------------------- + +Choosing a test framework is often contentious, so Django simply supports +both of the standard Python test frameworks. Choosing one is up to each +developer's personal tastes; each is supported equally. Since each test +system has different benefits, the best approach is probably to use both +together, picking the test system to match the type of tests you need to +write. + +For developers new to testing, however, this choice can seem +confusing, so here are a few key differences to help you decide weather +doctests or unit tests are 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 +there's no overhead of writing classes or methods; you simply put tests in +docstrings. This gives the added advantage of given your modules automatic +documentation -- well-written doctests can kill both the documentation and the +testing bird with a single stone. + +For developers 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. Since ``unittest`` is inspired by Java's JUnit, if +you've used testing frameworks in other languages that similarly were +inspired by JUnit, ``unittest`` should also feel pretty familiar. + +Since ``unittest`` is organized around classes and methods, if you need +to write a bunch of tests that all share similar code, you can easily use +subclass to abstract common tasks; this makes test code shorter and cleaner. +There's also support for explicit setup and/or cleanup routines, which give +you a high level of control over the environment your test cases run in. + +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. + +Testing utilities +================= + +Test Client +----------- + +A dummy browser; instruments the template generation process... + +Fixtures +-------- + +Feature still to come... + + +Running tests +============= + +Run your tests using your project's ``manage.py`` utility:: + + $ ./manage.py test + +If you only want to run tests for a particular application, add the +application name to the command line. For example, if your +``INSTALLED_APPS`` contains ``myproject.polls`` and ``myproject.animals``, +but you only want to run the animals unit tests, run:: + + $ ./manage.py test animals + +When you run your tests, you'll see a bunch of text flow by as the test +database is created and models are initialized. This test database is +created from scratch every time you run your tests. + +By default, the test database gets its name by prepending ``test_`` to +the database name specified by the ``DATABASE_NAME`` setting; all other +database settings will the same as they would be for the project normally. +If you wish to use a name other than the default for the test database, +you can use the ``TEST_DATABASE_NAME`` setting to provide a name. + +Once the test database has been established, Django will run your tests. +If everything goes well, at the end you'll see:: + + ---------------------------------------------------------------------- + Ran 22 tests in 0.221s + + OK + +If there are test failures, however, you'll see full details about what 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) + +When the tests have all been executed, the test database is destroyed. + +Using a different testing framework +=================================== + +Doctest and Unittest are not the only Python testing frameworks. While +Django doesn't provide explicit support these alternative frameworks, +it does provide a mechanism to allow you to invoke tests constructed for +an alternative framework as if they were normal Django tests. + +When you run ``./manage.py test``, Django looks at the ``TEST_RUNNER`` +setting to determine what to do. By default, ``TEST_RUNNER`` points to ``django.test.simple.run_tests``. This method defines the default Django +testing behaviour. This behaviour involves: + +#. Creating the test database +#. Running ``syncdb`` to install models and initial data into the test database +#. Looking for Unit Tests and Doctests in ``models.py`` and ``tests.py`` file for each installed application +#. Running the Unit Tests and Doctests that are found +#. Destroying the test database. + +If you define your own test runner method and point ``TEST_RUNNER`` +at that method, 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. + +Defining a test runner +---------------------- +By convention, a test runner should be called ``run_tests``; however, you +can call it anything you want. The only requirement is that it accept two +arguments: + +``run_tests(module_list, verbosity=1)`` +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The module list is the list of Python modules that contain the models to be +tested. This is the same format returned by ``django.db.models.get_apps()`` + +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. + +Testing utilities +----------------- + +To assist in the creation of your own test runner, Django provides +a number of utility methods in the ``django.test.utils`` module. + +``create_test_db(verbosity=1, autoclobber=False)``: +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Creates a new test database, and run ``syncdb`` against it. + +``verbosity`` has the same behaviour as in the test runner. + +``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. + +``create_test_db()`` has the side effect of modifying +``settings.DATABASE_NAME`` to match the name of the test database. + +``destroy_test_db(old_database_name, verbosity=1)``: +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Destroys the database with the name ``settings.DATABASE_NAME`` matching, +and restores the value of ``settings.DATABASE_NAME`` to the provided name. + +``verbosity`` has the same behaviour as in the test runner. |