Add Unit tests for CLI commands

[andrii-bodnar]

Currently, all the CLI commands are not covered by Unit tests. It's difficult to test these commands since it mocks the filesystem and console logs, so this leads to unexpected results and it's very hard to catch bugs during tests.

So this issue requires some refactoring of CLI in order to make it testable.

View the corresponding discussion in the Discord channel. It includes some possible ways how to solve this.

Current coverage of the CLI package - Codecov.