Failing test - getId() return string rather than integer

Hi,

I found an issue in a specific case, when you find a child entity (JOINED) which is linked to another child entity.

If I clone the linked child entity and call getId(), it gives the value as 'string' rather than 'integer'. If I set the property id as public, there is no problem.

If I call getId on the child entity rather than the clone, it gives 'integer' as expected. So it's weird...

This simple test demonstrates the problem.
Use `assertSame` instead, which avoids the check. Also add a failure message such as `'The identifier on the cloned instance is an integer'`