Missing tests

[MDeLuise]

Avoid duplicated feature requests

• There are no open or closed feature requests that are related to this request

Description

Currently, tests are missing in the system.
For the backend, the test directory has already a files' template useful to create unit and integration test.

Solution

Add unit and integration tests.

What are alternatives?

No response

Additional context

No response

[MDeLuise]

Issue partially fixed in #63, but as now:

• some unit tests are missing (backend),
• integration tests are missing (backend),
• all tests are missing (frontend)