Parameterized unit tests for Python - syntactic sugar inspired by https://chris-lamb.co.uk/posts/generating-dynamic-python-tests-using-metaclasses

parameterized.py

class ParameterizedTestsMeta(type):
    def __new__(cls, name, bases, attrs):
        skip_these_names = []
        i = 1
        for name, fn in attrs.items():
            if name.startswith('test_') and callable(fn) and getattr(fn, '_parameterized_params', None):
                skip_these_names.append(name)
                for params in fn._parameterized_params:
                    attrs['%s_%d' % (name, i)] = cls.make_parameterized_test(fn, params)
                    i += 1
        new_attrs = dict([
            pair for pair in attrs.items() if pair[0] not in skip_these_names
        ])
        return super(ParameterizedTestsMeta, cls).__new__(cls, name, bases, new_attrs)

    @classmethod
    def make_parameterized_test(cls, fn, params):
        def test_fn(self):
            fn(self, params)
        return test_fn

def parameterized(*params):
    def decorator(fn):
        fn._parameterized_params=params
        return fn
    return decorator

parameterized_example.py

import unittest
from parameterized import ParameterizedTestsMeta, parameterized

class DoubleTests(unittest.TestCase):
    __metaclass__ = ParameterizedTestsMeta

    @parameterized(
        (5, 10),
        (6, 12),
        (20, 40),
    )
    def test_double(self, (input, expected)):
        self.assertEqual(expected, double(input))

# The function we are testing
def double(i):
    return i * 2

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

Here's example output if we add another pair to the parameterized list of (30, 31):

$ python param.py
...F
======================================================================
FAIL: test_double_4 (__main__.test_double)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "param.py", line 21, in test_fn
    fn(self, params)
  File "param.py", line 40, in test_double
    self.assertEqual(expected, double(input))
AssertionError: 31 != 60

----------------------------------------------------------------------
Ran 4 tests in 0.000s

FAILED (failures=1)