TestProcess is incomaptible with setUpAll

[jakemac53]

Today, the heartbeat that TestProcess uses is incompatible with setUpAll, because it ends up running after setUpAll completes - and since setUpAll is expected to be "complete" after it finishes (notably not after tearDownAll completes) - then the first heartbeat to run will cause a test failure.

This is imo a core use case for TestProcess - you often want long lived processes that are shared across tests.