Add coverage reporting for `shunit2` Tests

[arthurbdiniz]

Description

To improve test quality and provide better insights into code coverage, we should add coverage reporting for our shunit2 tests.

Currently, the tests are executed using:

shunit2 ./tests/*

Integrating coverage reports will help identify untested parts of the codebase and guide further testing efforts.

Tasks

1. Investigate tools or approaches compatible with shunit2 for generating coverage reports.
2. Integrate coverage reporting into the CI workflow.
3. Ensure the reports are accessible (e.g., via artifacts or dashboards).
4. Validate the implementation to confirm accurate coverage reporting.