Feat: Tests for Fund Manager

[renzobanegass]

This is a Draft PR, I couldn't advance more than this, as I'm encountering myself with 2 difficulties:

• The class fundmanager is unaccesible from the test, unless I declare the module as public in lib.cairo.
• We are using snforge to test, I checked the documentation here for creating these tests but the version didn't match, so I tried using the version implemented in the docs, that made the code work but the deployment of the contract is not working properly.

I'll still be looking into this but I wanted to make a draft for you to see what I found and see if you can lend me some help with this.

Another solution could be using different tools for testing.

I'll only push one test because I see no reason to push the tests related to the functionality if the most basic test is not working.

[adrianvrj]

@renzobanegass thanks for your PR, @EmmanuelAR will review it asap