Parameterized testing with any Python test framework
Parameterized testing in Python sucks.
parameterized fixes that. For everything. Parameterized testing for nose, parameterized testing for py.test, parameterized testing for unittest.
# 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).
| Py2.6 | Py2.7 | Py3.4 | Py3.5 | Py3.6 | Py3.7 | Py3.8 | Py3.9 | PyPy | @mock.patch |
|
|---|---|---|---|---|---|---|---|---|---|---|
| nose | yes | yes | yes | yes | yes | yes | yes | yes | yes | yes |
| nose2 | yes | yes | yes | yes | yes | yes | yes | yes | yes | yes |
| py.test 2 | yes | yes | no* | no* | no* | no* | yes | yes | yes | yes |
| py.test 3 | yes | yes | yes | yes | yes | yes | yes | yes | yes | yes |
| py.test 4 | no** | no** | no** | no** | no** | no** | no** | no** | no** | no** |
| py.test fixtures | no† | no† | no† | no† | no† | no† | no† | no† | no† | no† |
|
unittest
(
@parameterized.expand)
|
yes | yes | yes | yes | yes | yes | yes | yes | yes | yes |
|
unittest2
(
@parameterized.expand)
|
yes | yes | yes | yes | yes | yes | yes | yes | yes | yes |
*: py.test 2 does does not appear to work (#71) under Python 3. Please comment on the related issues if you are affected.
**: py.test 4 is not yet supported (but coming!) in issue #34
†: py.test fixture support is documented in issue #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:
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:
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):
import unittest
from parameterized import parameterized
class AddTestCase(unittest.TestCase):
@parameterized.expand([
("2 and 3", 2, 3, 5),
("3 and 5", 2, 3, 5),
])
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.
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:
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:
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:
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:
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:
@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:
@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:
@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:
Update your requirements file, replacing
nose-parameterizedwithparameterized.Replace all references to
nose_parameterizedwithparameterized:$ perl -pi -e 's/nose_parameterized/parameterized/g' your-codebase/
You're done!
FAQ
-
What happened to
nose-parameterized? - Originally only nose was supported. But now everything is supported, and it only made sense to change the name!
- What do you mean when you say "nose is best supported"?
-
There are small caveates with
py.testandunittest:py.testdoes not show the parameter values (ex, it will showtest_add[0]instead oftest_add[1, 2, 3]), andunittest/unittest2do not support test generators so@parameterized.expandmust be used. -
Why not use
@pytest.mark.parametrize? -
Because spelling is difficult. Also,
parameterizeddoesn't require you to repeat argument names, and (usingparam) 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. Useparameterized(with the e) instead and you'll be all set.
15 Feb 1, 2022
1.1k Dec 30, 2022
4 Sep 22, 2022
997 Jan 6, 2023
5 Nov 14, 2022
14 Jan 25, 2022
12 Dec 4, 2022
5 Mar 13, 2022
2 Aug 3, 2022
963 Dec 28, 2022
325 Dec 30, 2022
1 Jul 11, 2022
7.7k Jan 7, 2023
1.7k Dec 24, 2022
8.2k Jan 3, 2023
122 Nov 22, 2022
802 Dec 31, 2022