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Parameterized testing with any Python test framework

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Parameterized testing with any Python test framework

.. image:: https://img.shields.io/pypi/v/parameterized.svg :alt: PyPI :target: https://pypi.org/project/parameterized/

.. image:: https://circleci.com/gh/wolever/parameterized.svg?style=svg :alt: Circle CI :target: https://circleci.com/gh/wolever/parameterized

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

# testmath.py from nose.tools import assertequal from parameterized import parameterized, parameterized_class

import unittest import math

@parameterized([ (2, 2, 4), (2, 3, 8), (1, 9, 1), (0, 9, 0), ]) def testpow(base, exponent, expected): assertequal(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 testfloor(self, name, input, expected): assertequal(math.floor(input), expected)

@parameterizedclass(('a', 'b', 'expectedsum', 'expectedproduct'), [ (1, 2, 3, 2), (5, 5, 10, 25), ]) class TestMathClass(unittest.TestCase): def testadd(self): assertequal(self.a + self.b, self.expectedsum)

  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://travis-ci.org/wolever/parameterized

.. list-table:: :header-rows: 1 :stub-columns: 1

  • -
    • 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
__

__ https://github.com/wolever/parameterized/issues/71 __ 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", 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.

.. 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 testgreaterthan_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 testsumsto_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 testmethod(self, param1, param2, ..., mockumask, mockfdopen, mockgetpid): ...

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

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.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.

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