Create Unit Tests

The Unit Tests that are currently in `lib_test.go` are kinda random, a bit all over the place and do not cover testing every corner case of every publicly exposed function (ie in testing parlance, we do not have 100% test coverage)

- Your task is to create a Unit Test to test every publicly exposed function
- The Unit Test _must_ cover every corner case (passing in edges that don't exist, boundary values etc)
- **Create a new issue** for the Unit Test you want to create _if it does not already exists._ As in, Check that the issue isn't a duplicate before creating!
- **No one shall be asssigned to this issue (#4)**

Start by reading the existing tests in lib_test.go and identifying the publicly exposed functions in the package. The issue asks for corner-case coverage for every public function, but does not name specific functions or expected behaviors, so a contributor would need to split this into smaller issues first. Done would mean a focused new issue and tests for one chosen public function's edge cases.

Escrita pelo modelo de indexação a partir do texto da issue.