What ability does this problem practice?

Verifying that a collection's decision about whether two items are the same behaves as intended.

What cases should the tests feed in?

Add the same content as two new instances and assert only one remains, that different products are each kept, and that removal works. Checking only with the same instance twice is not enough.

How do I run this problem?

The sandbox has no network access and dependencies are pre-fetched into the image. Run the tests with gradle test --offline --console=plain.

Wishlist Duplicates

Your task

Build a wishlist. Adding a product puts it in the list, and the same product (productId) stays as a single entry even when added twice. Removing works too. Complete Wishlist.

Ground rules

•Whether two items are the same product is decided by productId.
•Everything runs in memory (no storage).

Not required

•Persisting and loading the wishlist.
•Per-user lists and sharing.

▶About this challenge

Complete a plain-Java (no framework) Wishlist. The same product (by product number) stays a single entry even when added twice, different products are each kept, and removing works too. You practice verifying how a collection decides whether two items are the same.

When you put domain objects into a list or set, what matters is on what basis that collection decides whether two items are the same or different. If your notion of sameness lives in the content, you should trace how that basis is reflected in the code. Beyond adding different items, the habit of also checking the case of re-adding the same content as a new instance is the key. This problem deals with the area of how a collection decides whether two items are the same.

What ability does this problem practice?: Verifying that a collection's decision about whether two items are the same behaves as intended.
What cases should the tests feed in?: Add the same content as two new instances and assert only one remains, that different products are each kept, and that removal works. Checking only with the same instance twice is not enough.
How do I run this problem?: The sandbox has no network access and dependencies are pre-fetched into the image. Run the tests with gradle test --offline --console=plain.