assertMainThread

The test bypass used to cover the whole of an end-to-end run, which hid main-thread violations that crash in production, such as reading a Ref value during background layout. It is now scoped to the two callers that cannot satisfy the assertion: runs with no real main Looper (see hasRealMainLooper), and instrumentation test bodies, which drive Litho from the runner's own thread (see isInstrumentationThread).

Everything else, jest-e2e included, is held to the production contract.