Write base set of extra PublisherSubscriberTest for up-transport-zenoh-cpp

[gregmedd]

“Extra” tests in a transport library provide an opportunity to exercise end-to-end layer communication. Layer 2 tests do not contribute to coverage for transport libraries since transport implementations are entirely layer 1. However, layer 2 tests are critical in evaluating the health and performance of a transport implementation.

This test will validate the interoperability between Publisher and Subscriber over Zenoh. It should verify that published messages arrive with all data intact and are received only by the intended subscribers. Additionally, it should verify, to the extent possible, that messages can be exchanged between threads, processes, and across the (loopback) network. Where possible, it should also make assertions about performance and validate message handling under load.

[gregmedd]

#65 contained the bare minimum, but it should be expanded to check multiple publishers and subscribers and verify messages go to the right places.

[gregmedd]

Note: this has been split. This task will focus on just enough testing to move development forward, and the rest will be handled in #74

[billpittman]

I'll take this task.

[gregmedd]

@billpittman - Go for it. Note that a test already exists for this, so the P0 task is just to take a look at that and determine if any additional assertions or tests are critical to unblocking development right now. Extending it with full coverage of use cases and configurations can be handled in #74.

[billpittman]

Fixed by #92 at least for the basic tests.