Testing Helpers¶

chumicro_sockets.testing ships FakeSocket — an in-memory test double satisfying the duck-typed TCP socket surface (send / recv_into / close / setblocking) so downstream libraries (chumicro-mqtt, chumicro-requests) and your own network apps can reach high coverage without spinning up a network.

Usage¶

from chumicro_sockets.testing import FakeSocket


def test_handshake_writes_correct_prefix():
    sock = FakeSocket()
    # Script the response the server would have sent.
    sock.enqueue_recv(b"\x20\x02\x00\x00")  # MQTT CONNACK packet

    client = MQTTClient(sock)
    client.connect()

    # Assert what we sent.
    assert sock.sent.startswith(b"\x10")  # MQTT CONNECT packet prefix

FakeSocket.sent is a bytearray that accumulates every send() call. enqueue_recv(chunk) queues a chunk for the next recv_into(); multiple chunks queue in FIFO order. enqueue_eagain_for_send(count) and enqueue_eagain_for_recv(count) script OSError(EAGAIN) raises so non-blocking-loop logic can be exercised deterministically.

A short read pushes the unconsumed tail back on the queue head — mimics real-socket fragmentation:

sock = FakeSocket()
sock.enqueue_recv(b"abcdef")
buffer = bytearray(8)
sock.recv_into(buffer, 3)   # reads "abc"; "def" still queued
sock.recv_into(buffer, 8)   # reads "def"

Usage from other libraries¶

from chumicro_sockets.testing import FakeSocket

Project convention: libraries that expose injectable services ship their own test fakes alongside the production code.

API Reference¶