How to test that `clear` command is working correctly in BASH?

Now i try find the way to prove that a clear command is working correctly on my own REPL

Example

$ cd ~
$ pwd
/home/user
$ echo "hello"
hello

then type clear

$

but sometime some unexpected behavior is occurred after using a clear command

e.g.

[one blank line here]
$

A one blank line after using clear command is undesirable behavior and I hope this kind of bug can be detected automatically via a unit test. If you have any idea to prove that clear command is working correctly please purpose.