Define a function that computes the length of a given list or string
You can't use the builtin len function, you must use a for loop.

Example:

>>> length('hello')
5
import unittest


class LengthTestCase(unittest.TestCase):
    def test_length_multiple_words(self):
        self.assertEqual(length('hello world'), 11)

    def test_length_single_word(self):
        self.assertEqual(length('hello'), 5)

    def test_length_empty_string(self):
        self.assertEqual(length(''), 0)