Confused in List of 3 things

[AsadA969]

As far I know, If we are given a list of three things in a sentence then we should put COMMA before the final and.. But, the following sentence confused me. So, could you please eradicate my confusion?

A Christmas cracker usually contains a paper hat, a joke and a novelty. .
There is no comma (;) before the final AND of the above sentence.
The sentence is quoted from Cambridge Dictionary 3rd edition (please search the word ''novelty'')
Thanks.

[RonPurewal]

this is a non-issue, because the presence/absence of punctuation is NEVER tested on this exam.

[RonPurewal]

––– YOU DON'T NEED TO KNOW THIS FOR THE EXAM –––

this varies from country to country.

in most formal writing in the u.s. and canada, the comma is there.
in other anglophone countries it's less common.

this exam follows the most prevalent u.s. convention. thus, on this exam, the final comma will ALWAYS be there in any list of 3 or more items.

––– YOU DON'T NEED TO KNOW THIS FOR THE EXAM –––

[RonPurewal]

there's only one way in which this might come in handy on the exam.

specifically:
in any (correctly written) list of 3 or more items, GMAC will ALWAYS use a comma before 'and [last thing]'.
thus, it follows that...
if you see 'X, Y and Z', without a comma between 'Y' and 'and', then you're NOT looking at a list of 3 things.

this doesn't necessarily mean that the construction is wrong; it just means that the construction is not a list.
if the construction makes sense as something other than a list—e.g., if 'Y and Z' is a modifier of 'X'—then 'X, Y and Z' can still make perfect sense.

i gave examples here:
https://www.manhattanprep.com/gmat/foru ... tml#p94236