Add more test cases

[SIGMazer]

We need more test cases cover all the different data types and edge cases.

[leo-aa88]

Should we make a list of which edge cases we should cover?

[leo-aa88]

We should also write a how to contribute guide for newcomers on writing tests.

[SIGMazer]

Should we make a list of which edge cases we should cover?

I was thinking of something like dealing with large numbers, divided by negative, access empty array and comparison between different data types