How do you generate dynamic (parameterized) unit tests in Python?

This is called "parametrization".

There are several tools that support this approach. E.g.:

• pytest's decorator
• parameterized

The resulting code looks like this:

from parameterized import parameterized

class TestSequence(unittest.TestCase):
    @parameterized.expand([
        ["foo", "a", "a",],
        ["bar", "a", "b"],
        ["lee", "b", "b"],
    ])
    def test_sequence(self, name, a, b):
        self.assertEqual(a,b)

Which will generate the tests:

test_sequence_0_foo (__main__.TestSequence) ... ok
test_sequence_1_bar (__main__.TestSequence) ... FAIL
test_sequence_2_lee (__main__.TestSequence) ... ok

======================================================================
FAIL: test_sequence_1_bar (__main__.TestSequence)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/parameterized/parameterized.py", line 233, in <lambda>
    standalone_func = lambda *a: func(*(a + p.args), **p.kwargs)
  File "x.py", line 12, in test_sequence
    self.assertEqual(a,b)
AssertionError: 'a' != 'b'

For historical reasons I'll leave the original answer circa 2008):

I use something like this:

import unittest

l = [["foo", "a", "a",], ["bar", "a", "b"], ["lee", "b", "b"]]

class TestSequense(unittest.TestCase):
    pass

def test_generator(a, b):
    def test(self):
        self.assertEqual(a,b)
    return test

if __name__ == '__main__':
    for t in l:
        test_name = 'test_%s' % t[0]
        test = test_generator(t[1], t[2])
        setattr(TestSequense, test_name, test)
    unittest.main()

Using unittest (since 3.4)

Since Python 3.4, the standard library unittest package has the subTest context manager.

See the documentation:

• 26.4.7. Distinguishing test iterations using subtests
• subTest

Example:

from unittest import TestCase

param_list = [('a', 'a'), ('a', 'b'), ('b', 'b')]

class TestDemonstrateSubtest(TestCase):
    def test_works_as_expected(self):
        for p1, p2 in param_list:
            with self.subTest():
                self.assertEqual(p1, p2)

You can also specify a custom message and parameter values to subTest():

with self.subTest(msg="Checking if p1 equals p2", p1=p1, p2=p2):

Using nose

The nose testing framework supports this.

Example (the code below is the entire contents of the file containing the test):

param_list = [('a', 'a'), ('a', 'b'), ('b', 'b')]

def test_generator():
    for params in param_list:
        yield check_em, params[0], params[1]

def check_em(a, b):
    assert a == b

The output of the nosetests command:

> nosetests -v
testgen.test_generator('a', 'a') ... ok
testgen.test_generator('a', 'b') ... FAIL
testgen.test_generator('b', 'b') ... ok

======================================================================
FAIL: testgen.test_generator('a', 'b')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/lib/python2.5/site-packages/nose-0.10.1-py2.5.egg/nose/case.py", line 203, in runTest
    self.test(*self.arg)
  File "testgen.py", line 7, in check_em
    assert a == b
AssertionError

----------------------------------------------------------------------
Ran 3 tests in 0.006s

FAILED (failures=1)

You would benefit from trying the TestScenarios library.

testscenarios provides clean dependency injection for python unittest style tests. This can be used for interface testing (testing many implementations via a single test suite) or for classic dependency injection (provide tests with dependencies externally to the test code itself, allowing easy testing in different situations).

This is effectively the same as parameterized as mentioned in a previous answer, but specific to unittest:

def sub_test(param_list):
    """Decorates a test case to run it as a set of subtests."""

    def decorator(f):

        @functools.wraps(f)
        def wrapped(self):
            for param in param_list:
                with self.subTest(**param):
                    f(self, **param)

        return wrapped

    return decorator

Example usage:

class TestStuff(unittest.TestCase):
    @sub_test([
        dict(arg1='a', arg2='b'),
        dict(arg1='x', arg2='y'),
    ])
    def test_stuff(self, arg1, arg2):
        ...

I have found that this works well for my purposes, especially if I need to generate tests that do slightly difference processes on a collection of data.

import unittest

def rename(newName):
    def renamingFunc(func):
        func.__name__ == newName
        return func
    return renamingFunc

class TestGenerator(unittest.TestCase):

    TEST_DATA = {}

    @classmethod
    def generateTests(cls):
        for dataName, dataValue in TestGenerator.TEST_DATA:
            for func in cls.getTests(dataName, dataValue):
                setattr(cls, "test_{:s}_{:s}".format(func.__name__, dataName), func)

    @classmethod
    def getTests(cls):
        raise(NotImplementedError("This must be implemented"))

class TestCluster(TestGenerator):

    TEST_CASES = []

    @staticmethod
    def getTests(dataName, dataValue):

        def makeTest(case):

            @rename("{:s}".format(case["name"]))
            def test(self):
                # Do things with self, case, data
                pass

            return test

        return [makeTest(c) for c in TestCluster.TEST_CASES]

TestCluster.generateTests()

The TestGenerator class can be used to spawn different sets of test cases like TestCluster.

TestCluster can be thought of as an implementation of the TestGenerator interface.

I had trouble making these work for setUpClass.

Here's a version of Javier's answer that gives setUpClass access to dynamically allocated attributes.

import unittest


class GeneralTestCase(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        print ''
        print cls.p1
        print cls.p2

    def runTest1(self):
        self.assertTrue((self.p2 - self.p1) == 1)

    def runTest2(self):
        self.assertFalse((self.p2 - self.p1) == 2)


def load_tests(loader, tests, pattern):
    test_cases = unittest.TestSuite()
    for p1, p2 in [(1, 2), (3, 4)]:
        clsname = 'TestCase_{}_{}'.format(p1, p2)
        dct = {
            'p1': p1,
            'p2': p2,
        }
        cls = type(clsname, (GeneralTestCase,), dct)
        test_cases.addTest(cls('runTest1'))
        test_cases.addTest(cls('runTest2'))
    return test_cases

Outputs

1
2
..
3
4
..
----------------------------------------------------------------------
Ran 4 tests in 0.000s

OK

import unittest

def generator(test_class, a, b,c,d,name):
    def test(self):
        print('Testexecution=',name)
        print('a=',a)
        print('b=',b)
        print('c=',c)
        print('d=',d)

    return test

def add_test_methods(test_class):
    test_list = [[3,3,5,6, 'one'], [5,5,8,9, 'two'], [0,0,5,6, 'three'],[0,0,2,3,'Four']]
    for case in test_list:
        print('case=',case[0], case[1],case[2],case[3],case[4])
        test = generator(test_class, case[0], case[1],case[2],case[3],case[4])
        setattr(test_class, "test_%s" % case[4], test)


class TestAuto(unittest.TestCase):
    def setUp(self):
        print ('Setup')
        pass

    def tearDown(self):
        print ('TearDown')
        pass

add_test_methods(TestAuto)

if __name__ == '__main__':
    unittest.main(verbosity=1)