ipc_{core|transport_structured|session|shm}: Unit tests.

[ygoldfeld]

Filed by @ygoldfeld pre-open-source:

unit_test (and its helpers) extensively test ipc_shm_arena_lend (a/k/a IPC: SHM-jemalloc), which is the module dependent on all other modules. @echan-dev wrote this as a unit test (within GoogleTest framework), and in addition in my opinion several of the higher-level tests, such as the session-test, are effectively integration-testing all of the dependencies: ipc_core, ipc_transport_structured (it is used by tests for their purposes as well as inside ipc_shm_arena_lend impl internally), ipc_session (used to set-up interprocess communication); though ipc_shm not so much.

transport_test is an extensive integration test of all of the above. The scripted mode focuses on ipc_core (and is extensible, both with new commands and more scripts), while the exercise mode focuses on APIs in ipc_session, ipc_transport_structured, ipc_shm, and ipc_shm_arena_lend. Additional functional testing is in perf_demo as of this writing; surely there will be more.

In that sense IMO, subjectively speaking, the test coverage is pretty damned good, and my confidence in correctness is at a high level.

However, the ipc_* modules other than ipc_shm_arena_lend really should have direct representation in unit_test in the same way ipc_shm_arena_lend (a/k/a IPC: SHM-jemalloc) enjoys. I.e., more or less every class/function – at least public/protected APIs – should have a GoogleTest, similarly to what Mr. Chan did.