countdown.py

import io, sys

book_of_counts = [
    {
        "expect": """let's get ready to rumble 8
let's get ready to rumble 7
let's get ready to rumble 6
let's get ready to rumble 5
let's get ready to rumble 4
let's get ready to rumble 3
let's get ready to rumble 2
let's get ready to rumble 1
*rumbling sound*
""",
        "input": {
            "message": "let's get ready to rumble",
            "start": 8,
            "stop": 1,
            "completion_message": "*rumbling sound*",
        },
    },
    {
        "expect": """prepare to die in this many ways: 4
prepare to die in this many ways: 3
prepare to die in this many ways: 2
prepare to die in this many ways: 1
or not, I guess
""",
        "input": {
            "message": "prepare to die in this many ways:",
            "start": 5,
            "stop": 2,
            "completion_message": "or not, I guess",
        },
    },
    {
        "expect": """Getting ready to start in 9
Getting ready to start in 8
Getting ready to start in 7
Getting ready to start in 6
Getting ready to start in 5
Getting ready to start in 4
Getting ready to start in 3
Getting ready to start in 2
Getting ready to start in 1
Let's go!
""",
        "input": {
            "message": "Getting ready to start in",
            "start": 9,
            "stop": 1,
            "completion_message": "Let's go!",
        },
    },
]


def countdown(message, start, stop, completion_message):
    for i in range(stop - 1, start):
        print("{m} {i}".format(m=message, i=start - i))
    print(completion_message)


for c in book_of_counts:
    capturedOutput = io.StringIO()  # Create StringIO object
    sys.stdout = capturedOutput  #  and redirect stdout.

    countdown(**c["input"])

    sys.stdout = sys.__stdout__  # Reset redirect.

    test = c["expect"]
    if capturedOutput.getvalue() != test:
        print("Captured:\n" + capturedOutput.getvalue() + "|")  # Now works as before.
        print("Expected:\n" + test + "|")
    print(capturedOutput.getvalue() == test)

This is how I'm going to test the countdown function. It's a surprisingly tricky function, so I'm going to write some kind of explainer for it.