Test cases for Binary Search Tree (BST) remove function using linked lists C++

Question: What test cases should I use to test the remove function?

My Thoughts:

case 1: delete when no element is in the system.

case 2: delete when there is only one element in the system.

case 3: delete when the left side of the tree is empty.

case 4: delete when the right side of the tree is empty.