import unittest


def append_to(element, to=[]):
    """
    Append an element to a list.
    If not list provided, create a new list containing only the element.

    :param element: the thing to append
    :param to: the list to append it to
    :return: the list with the appended thing
    """
    to.append(element)
    return to


class TestAppendTo(unittest.TestCase):
    def test_append_to(self):
        r = append_to('a')
        self.assertListEqual(r, ['a'])

    def test_append_to_two(self):
        r = append_to('b')
        append_to('c', r)
        self.assertListEqual(r, ['b', 'c'])


unittest.main(exit=False)