If you're only holding data in your Entities your domain model will become anemic, because the encapsulation is broken and the behaviors are all defined outside the entity, far from where the data are declared.
The whole point of the Clean Architecture (and the Hexagonal Architecture, Onion Architecture, etc.) is to promote the Dependency Inversion Principle, the D in the SOLID acronyme. To do that, the outer layers need to depend on the the inner layers, not the opposite. That's why it's not only ok but necessary that your interactors depend on your entities. But your entities should not depend on your interactors.
Testing interactors means testing a whole use case, so that's totally intended to execute the code in your entities !
Hope it helps :)
