The test creates mock_transport = Mock(spec=AsyncHttpTransport) but the production code patch_loop_close() uses isinstance(client.transport, AsyncHttpTransport) to check if the transport is async. A Mock object with spec= does NOT satisfy isinstance checks - it only makes the mock have the same attributes/methods. Therefore, _flush() returns early at line 71-72 without calling close_async(), causing assert_called_once() to fail. The test needs to patch the isinstance check or use a real AsyncHttpTransport instance.

When httpcore.AsyncSOCKSProxy() raises a RuntimeError (indicating SOCKS support is not installed), the exception is caught and a warning is logged about 'Disabling proxy support', but the code then falls through without returning, causing execution to continue to line 960 which creates an AsyncConnectionPool without proxy settings. This bypasses the user's intended proxy configuration entirely, potentially leaking traffic that was meant to go through a SOCKS proxy - a security/privacy concern if the proxy was being used for anonymity or network isolation.

In AsyncWorker.kill(), a _TERMINATOR is added to the queue (line 220) but the queue reference is never cleared (self._queue = None is missing). If start() is called again, the old queue is reused (line 237 check fails), and the new consumer task will immediately process the stale terminator and exit. This makes the worker non-restartable without creating a new instance.

The f-string assertion message on lines 1905-1906 is missing a space between the two string parts. When should_be_socks_proxy is True/False and the assertion fails, the message will read "SOCKS == Truebut got" or "SOCKS == Falsebut got" instead of "SOCKS == True but got" or "SOCKS == False but got". This makes test failure messages harder to read.