For real projects, Python ships with unittest. Tests are methods of a class that inherits from unittest.TestCase, and it provides assert methods that give clear messages when they fail:

import unittest

def initials(name):
    return "".join(word[0].upper() for word in name.split())

class TestInitials(unittest.TestCase):
    def test_two_words(self):
        self.assertEqual(initials("ada lovelace"), "AL")

    def test_empty(self):
        self.assertEqual(initials(""), "")

    def test_capitals(self):
        self.assertEqual(initials("ALAN TURING"), "AT")

unittest.main(argv=["tests"], exit=False)

unittest.main finds every method whose name starts with test, runs them all (even after one fails), and reports a summary: a dot for each pass, and OK at the end. The report appears in red because unittest writes to the error stream, which is normal.

argv=["tests"], exit=False makes it behave inside a page like this one; in a script on your own computer you would just write unittest.main().