[Fix] ignore receiver detached from transport

[alli83]

Hello,

Issue explained here: #51

summary: In case there are transports (single or multiple) but also classes implementing ReceiverInterface without being attached to a transport, the registration of "the transport" is prevented because it implements receiverInterface but not transportInterface.

Proposal: Check if's a TransportInterface before calling register of testTransportRegistry

[kbond]

Thanks for the fix @alli83!

I'm not familiar with advanced messenger usage. I'm just curious, what's the use case for having a receiver that's not also a transport?

[alli83]

The data was already stored and there was just a need to use some messenger concepts in order to facilitate some data processing which consisted in setting up a process using these concepts like the Envelope, the Receiver etc.

imho, it might be a little bit a peculiar use case but it would be cool to avoid that the presence of these concepts, used rather individually, prevents from finding the transport that we really want to test.

Thanks for your feedback!

[kbond]

Thanks @alli83!