Create tests for Moenda

[matheusgr]

🚀 Feature

Create a basic test structure for Moenda.

Test some https://github.com/SPLAB-UFCG/Moenda/blob/master/src/util.js functions.

I would recommend the Jest framework.

Have you read the Contributing Guidelines on issues?

yep.

Motivation

We should create a strong test set for moenda to verify what we are doing.

Pitch

Unit tests are awesome! We should to more!