def addUpcBarcodeCheckDigit(barcode: str) -> str:
    """Adds the check digit to a UPC barcode."""
    evenChecks = [int(digit) for i, digit in enumerate(barcode) if i % 2 == 0]
    oddChecks = [int(digit) for i, digit in enumerate(barcode) if i % 2 != 0]
    evenTotal = sum(int(digit) for digit in evenChecks) * 3
    oddTotal = sum(int(digit) for digit in oddChecks)
    checkDigit = 10 - (evenTotal + oddTotal) % 10
    return barcode + (str(checkDigit) if checkDigit != 10 else "0")


print("Testing addUpcBarcodeCheckDigit()...", end="")
assert addUpcBarcodeCheckDigit("03600029145") == "036000291452"
assert addUpcBarcodeCheckDigit("11111111111") == "111111111117"
assert addUpcBarcodeCheckDigit("23232323232") == "232323232329"
assert addUpcBarcodeCheckDigit("12345678900") == "123456789005"
assert addUpcBarcodeCheckDigit("00000000000") == "000000000000"
print("Passed!")