Add unit tests for zmq_utils.py (PR #939)

[Copilot]

PR vllm-project#939 introduced zmq_utils.py with ZmqQueue - a queue-like wrapper around ZMQ sockets for IPC. This module had no test coverage.

Test Coverage

Added 17 tests in tests/entrypoints/test_zmq_utils.py:

• Initialization: bind/connect modes, timeout configuration, error handling for missing endpoint
• Queue operations: put(), put_nowait(), get(), get_nowait() with timeout variations
• State inspection: empty() method correctness
• Resource management: close() idempotency
• Data handling: multiple messages, diverse Python types (primitives, collections, None)
• Helper function: create_zmq_queue() behavior

Implementation

• Uses tmp_path fixture for unique IPC endpoints per test (prevents parallel test conflicts)
• Tests use PUSH/PULL socket pairs for message flow verification
• Validates Python queue exception compatibility (queue.Empty, queue.Full)

def test_put_and_get(self, zmq_context, unique_endpoint):
    """Test basic put and get operations."""
    endpoint = unique_endpoint
    server = ZmqQueue(zmq_context, zmq.PULL, bind=endpoint)
    client = ZmqQueue(zmq_context, zmq.PUSH, connect=endpoint)
    
    test_data = {"key": "value", "number": 42}
    client.put(test_data)
    received = server.get()
    assert received == test_data

Original prompt

Add UT for PR: vllm-project#939

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