In this part you are to develop a set of unit tests for a scientific calculator program written in JavaScript. At first run the program. Try to use it to calculate some expressions. Then try to understand how does it work. Finally:

$*$ Write a total of $9$ tests, organized into three sets.

$*$ Each test set should target one functional element of the program $($You cannot choose $+,-,/$ and $*)$

$*$ Write the code that allows the program to pass your tests.

$*$ Explain your approach in each test set. What was your strategy here?

$*$ Capture screenshots or console logs of the code before and after it passed the tests, showing the output of the unit testing library. Shorten the output to the most important part, where it lists the number of tests passed and failed.