Fix Stream Close Timeout & Error Handling for send_message

[seetadev]

1. Successful Stream Close Within Timeout

Purpose: Ensure send_message succeeds and does not raise an error under normal conditions.
Test Setup:

• Mock send_message to complete within 1 second.
• muxed_conn.is_shutting_down() returns False.

Expected Result:

• No exception is raised.
• Stream closes successfully within timeout.

2. Stream Close Times Out

Purpose: Verify that a TimeoutError is raised when send_message takes too long.
Test Setup:

• Mock send_message to block > 5 seconds (e.g., using await trio.sleep(6)).
• muxed_conn.is_shutting_down() returns False.

Expected Result:

• trio.TooSlowError is caught.
• A TimeoutError("Stream close timed out") is raised.

3. Muxed Connection Unavailable (Not Shutting Down)

Purpose: Ensure a RuntimeError is raised when the connection is unavailable unexpectedly.
Test Setup:

• Mock send_message to raise MuxedConnUnavailable.
• muxed_conn.is_shutting_down() returns False.

Expected Result:

• A RuntimeError("Failed to send close message: muxed connection unavailable") is raised.

4. Muxed Connection Unavailable (During Shutdown)

Purpose: Confirm that no error is raised if the connection is unavailable but shutting down.
Test Setup:

• Mock send_message to raise MuxedConnUnavailable.
• muxed_conn.is_shutting_down() returns True.

Expected Result:

• Exception is suppressed.
• Cleanup proceeds silently.

5. Unexpected Exception During send_message

Purpose: Ensure that unexpected exceptions are surfaced correctly.
Test Setup:

• Mock send_message to raise a generic exception (e.g., ValueError("boom")).

Expected Result:

• The exception is re-raised and not suppressed.

Optional Utility:

You can also use pytest-trio and unittest.mock.AsyncMock to easily simulate async behaviors.