203 lines
8.0 KiB
ReStructuredText
203 lines
8.0 KiB
ReStructuredText
|
|
.. _`unittest.TestCase`:
|
|
.. _`unittest`:
|
|
|
|
Support for unittest.TestCase / Integration of fixtures
|
|
=====================================================================
|
|
|
|
.. _`unittest.py style`: http://docs.python.org/library/unittest.html
|
|
|
|
``pytest`` has support for running Python `unittest.py style`_ tests.
|
|
It's meant for leveraging existing unittest-style projects
|
|
to use pytest features. Concretely, pytest will automatically
|
|
collect ``unittest.TestCase`` subclasses and their ``test`` methods in
|
|
test files. It will invoke typical setup/teardown methods and
|
|
generally try to make test suites written to run on unittest, to also
|
|
run using ``pytest``. We assume here that you are familiar with writing
|
|
``unittest.TestCase`` style tests and rather focus on
|
|
integration aspects.
|
|
|
|
Usage
|
|
-------------------------------------------------------------------
|
|
|
|
After :ref:`installation` type::
|
|
|
|
pytest
|
|
|
|
and you should be able to run your unittest-style tests if they
|
|
are contained in ``test_*`` modules. If that works for you then
|
|
you can make use of most :ref:`pytest features <features>`, for example
|
|
``--pdb`` debugging in failures, using :ref:`plain assert-statements <assert>`,
|
|
:ref:`more informative tracebacks <tbreportdemo>`, stdout-capturing or
|
|
distributing tests to multiple CPUs via the ``-nNUM`` option if you
|
|
installed the ``pytest-xdist`` plugin. Please refer to
|
|
the general ``pytest`` documentation for many more examples.
|
|
|
|
.. note::
|
|
|
|
Running tests from ``unittest.TestCase`` subclasses with ``--pdb`` will
|
|
disable tearDown and cleanup methods for the case that an Exception
|
|
occurs. This allows proper post mortem debugging for all applications
|
|
which have significant logic in their tearDown machinery. However,
|
|
supporting this feature has the following side effect: If people
|
|
overwrite ``unittest.TestCase`` ``__call__`` or ``run``, they need to
|
|
to overwrite ``debug`` in the same way (this is also true for standard
|
|
unittest).
|
|
|
|
Mixing pytest fixtures into unittest.TestCase style tests
|
|
-----------------------------------------------------------
|
|
|
|
Running your unittest with ``pytest`` allows you to use its
|
|
:ref:`fixture mechanism <fixture>` with ``unittest.TestCase`` style
|
|
tests. Assuming you have at least skimmed the pytest fixture features,
|
|
let's jump-start into an example that integrates a pytest ``db_class``
|
|
fixture, setting up a class-cached database object, and then reference
|
|
it from a unittest-style test::
|
|
|
|
# content of conftest.py
|
|
|
|
# we define a fixture function below and it will be "used" by
|
|
# referencing its name from tests
|
|
|
|
import pytest
|
|
|
|
@pytest.fixture(scope="class")
|
|
def db_class(request):
|
|
class DummyDB:
|
|
pass
|
|
# set a class attribute on the invoking test context
|
|
request.cls.db = DummyDB()
|
|
|
|
This defines a fixture function ``db_class`` which - if used - is
|
|
called once for each test class and which sets the class-level
|
|
``db`` attribute to a ``DummyDB`` instance. The fixture function
|
|
achieves this by receiving a special ``request`` object which gives
|
|
access to :ref:`the requesting test context <request-context>` such
|
|
as the ``cls`` attribute, denoting the class from which the fixture
|
|
is used. This architecture de-couples fixture writing from actual test
|
|
code and allows re-use of the fixture by a minimal reference, the fixture
|
|
name. So let's write an actual ``unittest.TestCase`` class using our
|
|
fixture definition::
|
|
|
|
# content of test_unittest_db.py
|
|
|
|
import unittest
|
|
import pytest
|
|
|
|
@pytest.mark.usefixtures("db_class")
|
|
class MyTest(unittest.TestCase):
|
|
def test_method1(self):
|
|
assert hasattr(self, "db")
|
|
assert 0, self.db # fail for demo purposes
|
|
|
|
def test_method2(self):
|
|
assert 0, self.db # fail for demo purposes
|
|
|
|
The ``@pytest.mark.usefixtures("db_class")`` class-decorator makes sure that
|
|
the pytest fixture function ``db_class`` is called once per class.
|
|
Due to the deliberately failing assert statements, we can take a look at
|
|
the ``self.db`` values in the traceback::
|
|
|
|
$ pytest test_unittest_db.py
|
|
======= test session starts ========
|
|
platform linux -- Python 3.5.2, pytest-3.0.5, py-1.4.31, pluggy-0.4.0
|
|
rootdir: $REGENDOC_TMPDIR, inifile:
|
|
collected 2 items
|
|
|
|
test_unittest_db.py FF
|
|
|
|
======= FAILURES ========
|
|
_______ MyTest.test_method1 ________
|
|
|
|
self = <test_unittest_db.MyTest testMethod=test_method1>
|
|
|
|
def test_method1(self):
|
|
assert hasattr(self, "db")
|
|
> assert 0, self.db # fail for demo purposes
|
|
E AssertionError: <conftest.db_class.<locals>.DummyDB object at 0xdeadbeef>
|
|
E assert 0
|
|
|
|
test_unittest_db.py:9: AssertionError
|
|
_______ MyTest.test_method2 ________
|
|
|
|
self = <test_unittest_db.MyTest testMethod=test_method2>
|
|
|
|
def test_method2(self):
|
|
> assert 0, self.db # fail for demo purposes
|
|
E AssertionError: <conftest.db_class.<locals>.DummyDB object at 0xdeadbeef>
|
|
E assert 0
|
|
|
|
test_unittest_db.py:12: AssertionError
|
|
======= 2 failed in 0.12 seconds ========
|
|
|
|
This default pytest traceback shows that the two test methods
|
|
share the same ``self.db`` instance which was our intention
|
|
when writing the class-scoped fixture function above.
|
|
|
|
|
|
autouse fixtures and accessing other fixtures
|
|
-------------------------------------------------------------------
|
|
|
|
Although it's usually better to explicitly declare use of fixtures you need
|
|
for a given test, you may sometimes want to have fixtures that are
|
|
automatically used in a given context. After all, the traditional
|
|
style of unittest-setup mandates the use of this implicit fixture writing
|
|
and chances are, you are used to it or like it.
|
|
|
|
You can flag fixture functions with ``@pytest.fixture(autouse=True)``
|
|
and define the fixture function in the context where you want it used.
|
|
Let's look at an ``initdir`` fixture which makes all test methods of a
|
|
``TestCase`` class execute in a temporary directory with a
|
|
pre-initialized ``samplefile.ini``. Our ``initdir`` fixture itself uses
|
|
the pytest builtin :ref:`tmpdir <tmpdir>` fixture to delegate the
|
|
creation of a per-test temporary directory::
|
|
|
|
# content of test_unittest_cleandir.py
|
|
import pytest
|
|
import unittest
|
|
|
|
class MyTest(unittest.TestCase):
|
|
@pytest.fixture(autouse=True)
|
|
def initdir(self, tmpdir):
|
|
tmpdir.chdir() # change to pytest-provided temporary directory
|
|
tmpdir.join("samplefile.ini").write("# testdata")
|
|
|
|
def test_method(self):
|
|
s = open("samplefile.ini").read()
|
|
assert "testdata" in s
|
|
|
|
Due to the ``autouse`` flag the ``initdir`` fixture function will be
|
|
used for all methods of the class where it is defined. This is a
|
|
shortcut for using a ``@pytest.mark.usefixtures("initdir")`` marker
|
|
on the class like in the previous example.
|
|
|
|
Running this test module ...::
|
|
|
|
$ pytest -q test_unittest_cleandir.py
|
|
.
|
|
1 passed in 0.12 seconds
|
|
|
|
... gives us one passed test because the ``initdir`` fixture function
|
|
was executed ahead of the ``test_method``.
|
|
|
|
.. note::
|
|
|
|
While pytest supports receiving fixtures via :ref:`test function arguments <funcargs>` for non-unittest test methods, ``unittest.TestCase`` methods cannot directly receive fixture
|
|
function arguments as implementing that is likely to inflict
|
|
on the ability to run general unittest.TestCase test suites.
|
|
Maybe optional support would be possible, though. If unittest finally
|
|
grows a plugin system that should help as well. In the meanwhile, the
|
|
above ``usefixtures`` and ``autouse`` examples should help to mix in
|
|
pytest fixtures into unittest suites. And of course you can also start
|
|
to selectively leave away the ``unittest.TestCase`` subclassing, use
|
|
plain asserts and get the unlimited pytest feature set.
|
|
|
|
|
|
Converting from unittest to pytest
|
|
---------------------------------------
|
|
|
|
If you want to convert your unittest testcases to pytest, there are
|
|
some helpers like `unittest2pytest
|
|
<https://pypi.python.org/pypi/unittest2pytest/>`__, which uses lib2to3
|
|
and introspection for the transformation.
|