How many test cases should there be to check adding to the cart?

Question

Software testing

Good evening. There is a website - an online store. Let's say there are 20 things in it, each thing has 5 sizes. You need to check adding the item to the cart. How many test cases should there be? Do you need to do a separate test case to add each item of each size to the basket, that is, 100 cases? Or take one thing of the same size, that is, 20 cases? Or is something else better? Tell me like science.
Thanks in advance.

Answer 1

In fact, in addition to the "add" action itself, there should be more cases.
For example, the re-adding of an already lying product in the basket, etc.
Answering your question, it depends.
There is such a term as "exhaustive testing" - when all possible options (combinations) of parameters that affect the expected result are sorted out. It's long, and most of the time it's pointless, but sometimes it applies.
To minimize the number of checks, there is a separate test design practice called Pairwise Testing:
qcthoughtsaloud.blogspot.ru/2010/06/pairwise-testi...
In your case, it makes sense to use it.