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Fix flaky test_ash_end_to_end #760

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Merged
puddly merged 1 commit into from
Sep 28, 2026
Merged

Fix flaky test_ash_end_to_end #760

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40 changes: 24 additions & 16 deletions tests/test_ash.py
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
from __future__ import annotations

import asyncio
from asyncio import timeout as asyncio_timeout
import logging
import random
from unittest.mock import MagicMock, call, patch
Expand Down Expand Up @@ -104,8 +105,10 @@ def write(self, data: bytes) -> None:


class FakeTransportRandomLoss(FakeTransport):
loss_rate: float = 0.20

def write(self, data: bytes) -> None:
if random.random() < 0.20:
if random.random() < self.loss_rate:
return

super().write(data)
Expand Down Expand Up @@ -541,13 +544,11 @@ async def test_ash_end_to_end(transport_cls: type[FakeTransport]) -> None:
ncp_ezsp.data_received.reset_mock()
host_ezsp.data_received.reset_mock()

# Let's let a request fail due to a connectivity issue
# Let's let a request fail due to a connectivity issue. The link stays down until
# every retry has timed out, however long that takes on a loaded machine.
with patch.object(ncp_transport, "paused", True):
send_task = asyncio.create_task(host.send_data(b"host failure"))
await asyncio.sleep(host._t_rx_ack * 15)

with pytest.raises(TimeoutError):
await send_task
with pytest.raises(TimeoutError):
await host.send_data(b"host failure")

ncp_ezsp.data_received.reset_mock()
host_ezsp.data_received.reset_mock()
Expand All @@ -569,11 +570,8 @@ async def test_ash_end_to_end(transport_cls: type[FakeTransport]) -> None:
assert ncp._ncp_reset_code is None

with patch.object(host_transport, "paused", True):
send_task = asyncio.create_task(ncp.send_data(b"ncp failure"))
await asyncio.sleep(ncp._t_rx_ack * 15)

with pytest.raises(TimeoutError):
await send_task
with pytest.raises(TimeoutError):
await ncp.send_data(b"ncp failure")

assert (
host._ncp_reset_code is t.NcpResetCode.ERROR_EXCEEDED_MAXIMUM_ACK_TIMEOUT_COUNT
Expand All @@ -590,14 +588,24 @@ async def test_ash_end_to_end(transport_cls: type[FakeTransport]) -> None:
await host.send_data(b"test")

host.send_reset()
await asyncio.sleep(0.01)

async with asyncio_timeout(1):
while host._ncp_state is not ash.NcpState.CONNECTED:
await asyncio.sleep(0)

await host.send_data(b"test")

# Trigger a failure caused by excessive NAKs
# Trigger a failure caused by excessive NAKs. The host's ACK timeout is kept far
# above the NCP's NAK delay and no frames are lost, so every attempt ends in a NAK
# and never in a timeout.
ncp._t_rx_ack = ash.T_RX_ACK_INIT / 1000
host._t_rx_ack = ash.T_RX_ACK_INIT / 1000
host._t_rx_ack = 5.0

with patch.object(ncp, "nak_state", True):
with (
patch("bellows.ash.T_RX_ACK_MAX", host._t_rx_ack),
patch.object(FakeTransportRandomLoss, "loss_rate", 0.0),
patch.object(ncp, "nak_state", True),
):
with pytest.raises(ash.NotAcked):
await host.send_data(b"ncp NAKing until failure")

Expand Down
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