Parameterized testing with any Python test framework
====================================================
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Parameterized testing in Python sucks.
``parameterized`` fixes that. For everything. Parameterized testing for nose,
parameterized testing for py.test, parameterized testing for unittest.
.. code:: python
# test_math.py
from nose.tools import assert_equal
from parameterized import parameterized, parameterized_class
import unittest
import math
@parameterized([
(2, 2, 4),
(2, 3, 8),
(1, 9, 1),
(0, 9, 0),
])
def test_pow(base, exponent, expected):
assert_equal(math.pow(base, exponent), expected)
class TestMathUnitTest(unittest.TestCase):
@parameterized.expand([
("negative", -1.5, -2.0),
("integer", 1, 1.0),
("large fraction", 1.6, 1),
])
def test_floor(self, name, input, expected):
assert_equal(math.floor(input), expected)
@parameterized_class(('a', 'b', 'expected_sum', 'expected_product'), [
(1, 2, 3, 2),
(5, 5, 10, 25),
])
class TestMathClass(unittest.TestCase):
def test_add(self):
assert_equal(self.a + self.b, self.expected_sum)
def test_multiply(self):
assert_equal(self.a * self.b, self.expected_product)
@parameterized_class([
{ "a": 3, "expected": 2 },
{ "b": 5, "expected": -4 },
])
class TestMathClassDict(unittest.TestCase):
a = 1
b = 1
def test_subtract(self):
assert_equal(self.a - self.b, self.expected)
With nose (and nose2)::
$ nosetests -v test_math.py
test_floor_0_negative (test_math.TestMathUnitTest) ... ok
test_floor_1_integer (test_math.TestMathUnitTest) ... ok
test_floor_2_large_fraction (test_math.TestMathUnitTest) ... ok
test_math.test_pow(2, 2, 4, {}) ... ok
test_math.test_pow(2, 3, 8, {}) ... ok
test_math.test_pow(1, 9, 1, {}) ... ok
test_math.test_pow(0, 9, 0, {}) ... ok
test_add (test_math.TestMathClass_0) ... ok
test_multiply (test_math.TestMathClass_0) ... ok
test_add (test_math.TestMathClass_1) ... ok
test_multiply (test_math.TestMathClass_1) ... ok
test_subtract (test_math.TestMathClassDict_0) ... ok
----------------------------------------------------------------------
Ran 12 tests in 0.015s
OK
As the package name suggests, nose is best supported and will be used for all
further examples.
With py.test (version 2.0 and above)::
$ py.test -v test_math.py
============================= test session starts ==============================
platform darwin -- Python 3.6.1, pytest-3.1.3, py-1.4.34, pluggy-0.4.0
collecting ... collected 13 items
test_math.py::test_pow::[0] PASSED
test_math.py::test_pow::[1] PASSED
test_math.py::test_pow::[2] PASSED
test_math.py::test_pow::[3] PASSED
test_math.py::TestMathUnitTest::test_floor_0_negative PASSED
test_math.py::TestMathUnitTest::test_floor_1_integer PASSED
test_math.py::TestMathUnitTest::test_floor_2_large_fraction PASSED
test_math.py::TestMathClass_0::test_add PASSED
test_math.py::TestMathClass_0::test_multiply PASSED
test_math.py::TestMathClass_1::test_add PASSED
test_math.py::TestMathClass_1::test_multiply PASSED
test_math.py::TestMathClassDict_0::test_subtract PASSED
==================== 12 passed, 4 warnings in 0.16 seconds =====================
With unittest (and unittest2)::
$ python -m unittest -v test_math
test_floor_0_negative (test_math.TestMathUnitTest) ... ok
test_floor_1_integer (test_math.TestMathUnitTest) ... ok
test_floor_2_large_fraction (test_math.TestMathUnitTest) ... ok
test_add (test_math.TestMathClass_0) ... ok
test_multiply (test_math.TestMathClass_0) ... ok
test_add (test_math.TestMathClass_1) ... ok
test_multiply (test_math.TestMathClass_1) ... ok
test_subtract (test_math.TestMathClassDict_0) ... ok
----------------------------------------------------------------------
Ran 8 tests in 0.001s
OK
(note: because unittest does not support test decorators, only tests created
with ``@parameterized.expand`` will be executed)
With green::
$ green test_math.py -vvv
test_math
TestMathClass_1
. test_method_a
. test_method_b
TestMathClass_2
. test_method_a
. test_method_b
TestMathClass_3
. test_method_a
. test_method_b
TestMathUnitTest
. test_floor_0_negative
. test_floor_1_integer
. test_floor_2_large_fraction
TestMathClass_0
. test_add
. test_multiply
TestMathClass_1
. test_add
. test_multiply
TestMathClassDict_0
. test_subtract
Ran 12 tests in 0.121s
OK (passes=9)
Installation
------------
::
$ pip install parameterized
Compatibility
-------------
`Yes`__ (mostly).
__ https://app.circleci.com/pipelines/github/wolever/parameterized?branch=master
.. list-table::
:header-rows: 1
:stub-columns: 1
* -
- Py3.7
- Py3.8
- Py3.9
- Py3.10
- Py3.11
- PyPy3
- ``@mock.patch``
* - nose
- yes
- yes
- yes
- yes
- no§
- no§
- yes
* - nose2
- yes
- yes
- yes
- yes
- yes
- yes
- yes
* - py.test 2
- no*
- no*
- no*
- no*
- no*
- no*
- no*
* - py.test 3
- yes
- yes
- yes
- yes
- no*
- no*
- yes
* - py.test 4
- no**
- no**
- no**
- no**
- no**
- no**
- no**
* - py.test fixtures
- no†
- no†
- no†
- no†
- no†
- no†
- no†
* - | unittest
| (``@parameterized.expand``)
- yes
- yes
- yes
- yes
- yes
- yes
- yes
* - | unittest2
| (``@parameterized.expand``)
- yes
- yes
- yes
- yes
- no§
- no§
- yes
§: nose and unittest2 - both of which were last updated in 2015 - sadly do not
appear to support Python 3.10 or 3.11.
\*: `py.test 2 does not appear to work under Python 3 (#71)`__, and
`py.test 3 does not appear to work under Python 3.10 or 3.11 (#154)`__.
\*\*: py.test 4 is not yet supported (but coming!) in `issue #34`__
†: py.test fixture support is documented in `issue #81`__
__ https://github.com/wolever/parameterized/issues/71
__ https://github.com/wolever/parameterized/issues/154
__ https://github.com/wolever/parameterized/issues/34
__ https://github.com/wolever/parameterized/issues/81
Dependencies
------------
(this section left intentionally blank)
Exhaustive Usage Examples
--------------------------
The ``@parameterized`` and ``@parameterized.expand`` decorators accept a list
or iterable of tuples or ``param(...)``, or a callable which returns a list or
iterable:
.. code:: python
from parameterized import parameterized, param
# A list of tuples
@parameterized([
(2, 3, 5),
(3, 5, 8),
])
def test_add(a, b, expected):
assert_equal(a + b, expected)
# A list of params
@parameterized([
param("10", 10),
param("10", 16, base=16),
])
def test_int(str_val, expected, base=10):
assert_equal(int(str_val, base=base), expected)
# An iterable of params
@parameterized(
param.explicit(*json.loads(line))
for line in open("testcases.jsons")
)
def test_from_json_file(...):
...
# A callable which returns a list of tuples
def load_test_cases():
return [
("test1", ),
("test2", ),
]
@parameterized(load_test_cases)
def test_from_function(name):
...
.. **
Note that, when using an iterator or a generator, all the items will be loaded
into memory before the start of the test run (we do this explicitly to ensure
that generators are exhausted exactly once in multi-process or multi-threaded
testing environments).
The ``@parameterized`` decorator can be used test class methods, and standalone
functions:
.. code:: python
from parameterized import parameterized
class AddTest(object):
@parameterized([
(2, 3, 5),
])
def test_add(self, a, b, expected):
assert_equal(a + b, expected)
@parameterized([
(2, 3, 5),
])
def test_add(a, b, expected):
assert_equal(a + b, expected)
And ``@parameterized.expand`` can be used to generate test methods in
situations where test generators cannot be used (for example, when the test
class is a subclass of ``unittest.TestCase``):
.. code:: python
import unittest
from parameterized import parameterized
class AddTestCase(unittest.TestCase):
@parameterized.expand([
("2 and 3", 2, 3, 5),
("3 and 5", 3, 5, 8),
])
def test_add(self, _, a, b, expected):
assert_equal(a + b, expected)
Will create the test cases::
$ nosetests example.py
test_add_0_2_and_3 (example.AddTestCase) ... ok
test_add_1_3_and_5 (example.AddTestCase) ... ok
----------------------------------------------------------------------
Ran 2 tests in 0.001s
OK
Note that ``@parameterized.expand`` works by creating new methods on the test
class. If the first parameter is a string, that string will be added to the end
of the method name. For example, the test case above will generate the methods
``test_add_0_2_and_3`` and ``test_add_1_3_and_5``.
The names of the test cases generated by ``@parameterized.expand`` can be
customized using the ``name_func`` keyword argument. The value should
be a function which accepts three arguments: ``testcase_func``, ``param_num``,
and ``params``, and it should return the name of the test case.
``testcase_func`` will be the function to be tested, ``param_num`` will be the
index of the test case parameters in the list of parameters, and ``param``
(an instance of ``param``) will be the parameters which will be used.
.. code:: python
import unittest
from parameterized import parameterized
def custom_name_func(testcase_func, param_num, param):
return "%s_%s" %(
testcase_func.__name__,
parameterized.to_safe_name("_".join(str(x) for x in param.args)),
)
class AddTestCase(unittest.TestCase):
@parameterized.expand([
(2, 3, 5),
(2, 3, 5),
], name_func=custom_name_func)
def test_add(self, a, b, expected):
assert_equal(a + b, expected)
Will create the test cases::
$ nosetests example.py
test_add_1_2_3 (example.AddTestCase) ... ok
test_add_2_3_5 (example.AddTestCase) ... ok
----------------------------------------------------------------------
Ran 2 tests in 0.001s
OK
The ``param(...)`` helper class stores the parameters for one specific test
case. It can be used to pass keyword arguments to test cases:
.. code:: python
from parameterized import parameterized, param
@parameterized([
param("10", 10),
param("10", 16, base=16),
])
def test_int(str_val, expected, base=10):
assert_equal(int(str_val, base=base), expected)
If test cases have a docstring, the parameters for that test case will be
appended to the first line of the docstring. This behavior can be controlled
with the ``doc_func`` argument:
.. code:: python
from parameterized import parameterized
@parameterized([
(1, 2, 3),
(4, 5, 9),
])
def test_add(a, b, expected):
""" Test addition. """
assert_equal(a + b, expected)
def my_doc_func(func, num, param):
return "%s: %s with %s" %(num, func.__name__, param)
@parameterized([
(5, 4, 1),
(9, 6, 3),
], doc_func=my_doc_func)
def test_subtraction(a, b, expected):
assert_equal(a - b, expected)
::
$ nosetests example.py
Test addition. [with a=1, b=2, expected=3] ... ok
Test addition. [with a=4, b=5, expected=9] ... ok
0: test_subtraction with param(*(5, 4, 1)) ... ok
1: test_subtraction with param(*(9, 6, 3)) ... ok
----------------------------------------------------------------------
Ran 4 tests in 0.001s
OK
Finally ``@parameterized_class`` parameterizes an entire class, using
either a list of attributes, or a list of dicts that will be applied to the
class:
.. code:: python
from yourapp.models import User
from parameterized import parameterized_class
@parameterized_class([
{ "username": "user_1", "access_level": 1 },
{ "username": "user_2", "access_level": 2, "expected_status_code": 404 },
])
class TestUserAccessLevel(TestCase):
expected_status_code = 200
def setUp(self):
self.client.force_login(User.objects.get(username=self.username)[0])
def test_url_a(self):
response = self.client.get('/url')
self.assertEqual(response.status_code, self.expected_status_code)
def tearDown(self):
self.client.logout()
@parameterized_class(("username", "access_level", "expected_status_code"), [
("user_1", 1, 200),
("user_2", 2, 404)
])
class TestUserAccessLevel(TestCase):
def setUp(self):
self.client.force_login(User.objects.get(username=self.username)[0])
def test_url_a(self):
response = self.client.get("/url")
self.assertEqual(response.status_code, self.expected_status_code)
def tearDown(self):
self.client.logout()
The ``@parameterized_class`` decorator accepts a ``class_name_func`` argument,
which controls the name of the parameterized classes generated by
``@parameterized_class``:
.. code:: python
from parameterized import parameterized, parameterized_class
def get_class_name(cls, num, params_dict):
# By default the generated class named includes either the "name"
# parameter (if present), or the first string value. This example shows
# multiple parameters being included in the generated class name:
return "%s_%s_%s%s" %(
cls.__name__,
num,
parameterized.to_safe_name(params_dict['a']),
parameterized.to_safe_name(params_dict['b']),
)
@parameterized_class([
{ "a": "hello", "b": " world!", "expected": "hello world!" },
{ "a": "say ", "b": " cheese :)", "expected": "say cheese :)" },
], class_name_func=get_class_name)
class TestConcatenation(TestCase):
def test_concat(self):
self.assertEqual(self.a + self.b, self.expected)
::
$ nosetests -v test_math.py
test_concat (test_concat.TestConcatenation_0_hello_world_) ... ok
test_concat (test_concat.TestConcatenation_0_say_cheese__) ... ok
Using with Single Parameters
............................
If a test function only accepts one parameter and the value is not iterable,
then it is possible to supply a list of values without wrapping each one in a
tuple:
.. code:: python
@parameterized([1, 2, 3])
def test_greater_than_zero(value):
assert value > 0
Note, however, that if the single parameter *is* iterable (such as a list or
tuple), then it *must* be wrapped in a tuple, list, or the ``param(...)``
helper:
.. code:: python
@parameterized([
([1, 2, 3], ),
([3, 3], ),
([6], ),
])
def test_sums_to_6(numbers):
assert sum(numbers) == 6
(note, also, that Python requires single element tuples to be defined with a
trailing comma: ``(foo, )``)
Using with ``@mock.patch``
..........................
``parameterized`` can be used with ``mock.patch``, but the argument ordering
can be confusing. The ``@mock.patch(...)`` decorator must come *below* the
``@parameterized(...)``, and the mocked parameters must come *last*:
.. code:: python
@mock.patch("os.getpid")
class TestOS(object):
@parameterized(...)
@mock.patch("os.fdopen")
@mock.patch("os.umask")
def test_method(self, param1, param2, ..., mock_umask, mock_fdopen, mock_getpid):
...
Note: the same holds true when using ``@parameterized.expand``.
Migrating from ``nose-parameterized`` to ``parameterized``
----------------------------------------------------------
To migrate a codebase from ``nose-parameterized`` to ``parameterized``:
1. Update your requirements file, replacing ``nose-parameterized`` with
``parameterized``.
2. Replace all references to ``nose_parameterized`` with ``parameterized``::
$ perl -pi -e 's/nose_parameterized/parameterized/g' your-codebase/
3. You're done!
FAQ
---
What happened to Python 2.X, 3.5, and 3.6 support?
As of version 0.9.0, ``parameterized`` no longer supports Python 2.X, 3.5,
or 3.6. Previous versions of ``parameterized`` - 0.8.1 being the latest -
will continue to work, but will not receive any new features or bug fixes.
What do you mean when you say "nose is best supported"?
There are small caveates with ``py.test`` and ``unittest``: ``py.test``
does not show the parameter values (ex, it will show ``test_add[0]``
instead of ``test_add[1, 2, 3]``), and ``unittest``/``unittest2`` do not
support test generators so ``@parameterized.expand`` must be used.
Why not use ``@pytest.mark.parametrize``?
Because spelling is difficult. Also, ``parameterized`` doesn't require you
to repeat argument names, and (using ``param``) it supports optional
keyword arguments.
Why do I get an ``AttributeError: 'function' object has no attribute 'expand'`` with ``@parameterized.expand``?
You've likely installed the ``parametrized`` (note the missing *e*)
package. Use ``parameterized`` (with the *e*) instead and you'll be all
set.
What happened to ``nose-parameterized``?
Originally only nose was supported. But now everything is supported, and it
only made sense to change the name!