218 lines
7.6 KiB
ReStructuredText
218 lines
7.6 KiB
ReStructuredText
|
|
.. _`test generators`:
|
|
.. _`parametrizing-tests`:
|
|
.. _`parametrized test functions`:
|
|
.. _`parametrize`:
|
|
|
|
.. _`parametrize-basics`:
|
|
|
|
Parametrizing fixtures and test functions
|
|
==========================================================================
|
|
|
|
pytest enables test parametrization at several levels:
|
|
|
|
- :py:func:`pytest.fixture` allows one to :ref:`parametrize fixture
|
|
functions <fixture-parametrize>`.
|
|
|
|
* `@pytest.mark.parametrize`_ allows one to define multiple sets of
|
|
arguments and fixtures at the test function or class.
|
|
|
|
* `pytest_generate_tests`_ allows one to define custom parametrization
|
|
schemes or extensions.
|
|
|
|
.. _parametrizemark:
|
|
.. _`@pytest.mark.parametrize`:
|
|
|
|
|
|
``@pytest.mark.parametrize``: parametrizing test functions
|
|
---------------------------------------------------------------------
|
|
|
|
.. regendoc: wipe
|
|
|
|
.. versionadded:: 2.2
|
|
.. versionchanged:: 2.4
|
|
Several improvements.
|
|
|
|
The builtin ``pytest.mark.parametrize`` decorator enables
|
|
parametrization of arguments for a test function. Here is a typical example
|
|
of a test function that implements checking that a certain input leads
|
|
to an expected output::
|
|
|
|
# content of test_expectation.py
|
|
import pytest
|
|
@pytest.mark.parametrize("test_input,expected", [
|
|
("3+5", 8),
|
|
("2+4", 6),
|
|
("6*9", 42),
|
|
])
|
|
def test_eval(test_input, expected):
|
|
assert eval(test_input) == expected
|
|
|
|
Here, the ``@parametrize`` decorator defines three different ``(test_input,expected)``
|
|
tuples so that the ``test_eval`` function will run three times using
|
|
them in turn::
|
|
|
|
$ pytest
|
|
=========================== test session starts ============================
|
|
platform linux -- Python 3.x.y, pytest-3.x.y, py-1.x.y, pluggy-0.x.y
|
|
rootdir: $REGENDOC_TMPDIR, inifile:
|
|
collected 3 items
|
|
|
|
test_expectation.py ..F [100%]
|
|
|
|
================================= FAILURES =================================
|
|
____________________________ test_eval[6*9-42] _____________________________
|
|
|
|
test_input = '6*9', expected = 42
|
|
|
|
@pytest.mark.parametrize("test_input,expected", [
|
|
("3+5", 8),
|
|
("2+4", 6),
|
|
("6*9", 42),
|
|
])
|
|
def test_eval(test_input, expected):
|
|
> assert eval(test_input) == expected
|
|
E AssertionError: assert 54 == 42
|
|
E + where 54 = eval('6*9')
|
|
|
|
test_expectation.py:8: AssertionError
|
|
==================== 1 failed, 2 passed in 0.12 seconds ====================
|
|
|
|
As designed in this example, only one pair of input/output values fails
|
|
the simple test function. And as usual with test function arguments,
|
|
you can see the ``input`` and ``output`` values in the traceback.
|
|
|
|
Note that you could also use the parametrize marker on a class or a module
|
|
(see :ref:`mark`) which would invoke several functions with the argument sets.
|
|
|
|
It is also possible to mark individual test instances within parametrize,
|
|
for example with the builtin ``mark.xfail``::
|
|
|
|
# content of test_expectation.py
|
|
import pytest
|
|
@pytest.mark.parametrize("test_input,expected", [
|
|
("3+5", 8),
|
|
("2+4", 6),
|
|
pytest.param("6*9", 42,
|
|
marks=pytest.mark.xfail),
|
|
])
|
|
def test_eval(test_input, expected):
|
|
assert eval(test_input) == expected
|
|
|
|
Let's run this::
|
|
|
|
$ pytest
|
|
=========================== test session starts ============================
|
|
platform linux -- Python 3.x.y, pytest-3.x.y, py-1.x.y, pluggy-0.x.y
|
|
rootdir: $REGENDOC_TMPDIR, inifile:
|
|
collected 3 items
|
|
|
|
test_expectation.py ..x [100%]
|
|
|
|
=================== 2 passed, 1 xfailed in 0.12 seconds ====================
|
|
|
|
The one parameter set which caused a failure previously now
|
|
shows up as an "xfailed (expected to fail)" test.
|
|
|
|
To get all combinations of multiple parametrized arguments you can stack
|
|
``parametrize`` decorators::
|
|
|
|
import pytest
|
|
@pytest.mark.parametrize("x", [0, 1])
|
|
@pytest.mark.parametrize("y", [2, 3])
|
|
def test_foo(x, y):
|
|
pass
|
|
|
|
This will run the test with the arguments set to ``x=0/y=2``,``x=1/y=2``,
|
|
``x=0/y=3``, and ``x=1/y=3`` exhausting parameters in the order of the decorators.
|
|
|
|
.. _`pytest_generate_tests`:
|
|
|
|
Basic ``pytest_generate_tests`` example
|
|
---------------------------------------------
|
|
|
|
Sometimes you may want to implement your own parametrization scheme
|
|
or implement some dynamism for determining the parameters or scope
|
|
of a fixture. For this, you can use the ``pytest_generate_tests`` hook
|
|
which is called when collecting a test function. Through the passed in
|
|
``metafunc`` object you can inspect the requesting test context and, most
|
|
importantly, you can call ``metafunc.parametrize()`` to cause
|
|
parametrization.
|
|
|
|
For example, let's say we want to run a test taking string inputs which
|
|
we want to set via a new ``pytest`` command line option. Let's first write
|
|
a simple test accepting a ``stringinput`` fixture function argument::
|
|
|
|
# content of test_strings.py
|
|
|
|
def test_valid_string(stringinput):
|
|
assert stringinput.isalpha()
|
|
|
|
Now we add a ``conftest.py`` file containing the addition of a
|
|
command line option and the parametrization of our test function::
|
|
|
|
# content of conftest.py
|
|
|
|
def pytest_addoption(parser):
|
|
parser.addoption("--stringinput", action="append", default=[],
|
|
help="list of stringinputs to pass to test functions")
|
|
|
|
def pytest_generate_tests(metafunc):
|
|
if 'stringinput' in metafunc.fixturenames:
|
|
metafunc.parametrize("stringinput",
|
|
metafunc.config.getoption('stringinput'))
|
|
|
|
If we now pass two stringinput values, our test will run twice::
|
|
|
|
$ pytest -q --stringinput="hello" --stringinput="world" test_strings.py
|
|
.. [100%]
|
|
2 passed in 0.12 seconds
|
|
|
|
Let's also run with a stringinput that will lead to a failing test::
|
|
|
|
$ pytest -q --stringinput="!" test_strings.py
|
|
F [100%]
|
|
================================= FAILURES =================================
|
|
___________________________ test_valid_string[!] ___________________________
|
|
|
|
stringinput = '!'
|
|
|
|
def test_valid_string(stringinput):
|
|
> assert stringinput.isalpha()
|
|
E AssertionError: assert False
|
|
E + where False = <built-in method isalpha of str object at 0xdeadbeef>()
|
|
E + where <built-in method isalpha of str object at 0xdeadbeef> = '!'.isalpha
|
|
|
|
test_strings.py:3: AssertionError
|
|
1 failed in 0.12 seconds
|
|
|
|
As expected our test function fails.
|
|
|
|
If you don't specify a stringinput it will be skipped because
|
|
``metafunc.parametrize()`` will be called with an empty parameter
|
|
list::
|
|
|
|
$ pytest -q -rs test_strings.py
|
|
s [100%]
|
|
========================= short test summary info ==========================
|
|
SKIP [1] test_strings.py: got empty parameter set ['stringinput'], function test_valid_string at $REGENDOC_TMPDIR/test_strings.py:1
|
|
1 skipped in 0.12 seconds
|
|
|
|
Note that when calling ``metafunc.parametrize`` multiple times with different parameter sets, all parameter names across
|
|
those sets cannot be duplicated, otherwise an error will be raised.
|
|
|
|
More examples
|
|
-------------
|
|
|
|
For further examples, you might want to look at :ref:`more
|
|
parametrization examples <paramexamples>`.
|
|
|
|
.. _`metafunc object`:
|
|
|
|
The **metafunc** object
|
|
-------------------------------------------
|
|
|
|
.. currentmodule:: _pytest.python
|
|
.. autoclass:: Metafunc
|
|
:members:
|