not complete test coverage

**Describe the bug**
We need to add more tests, that will shield us from simple errors that we may have.
This task is just an example about how tests can protect us.

And our CI right now told us that all is fine:
But it's not. Actual PR is here: https://github.com/GroceriStar/sd/pull/363

**Expected behavior**
We should review our module and chat about what quick and simple tests we should add here in order to get a quick boost in the quality of our module. Why quick? because everyone is busy and it's better to have few simple solutions instead of one long, that will take few weeks to complete(which is not real with our current low-level of the complexity of this methods.)

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Additional context**
Add any other context about the problem here.