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fix(vrf): raise NoValidatorsAvailableError when total_stake is zero #1735

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fix(vrf): raise NoValidatorsAvailableError when total_stake is zero #1735

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d5a5f11
fix(vrf): raise NoValidatorsAvailableError when total_stake is zero (…
Sertug17 Aug 15, 2026
8b84101
style: add return type annotation to test function (CodeRabbit review)
Sertug17 Aug 15, 2026
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6 changes: 5 additions & 1 deletion backend/consensus/vrf.py
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
from datetime import datetime
import numpy as np
from backend.consensus.base import DEFAULT_VALIDATORS_COUNT
from backend.consensus.base import DEFAULT_VALIDATORS_COUNT, NoValidatorsAvailableError


def get_validators_for_transaction(
Expand All @@ -18,6 +18,10 @@ def get_validators_for_transaction(
num_validators = min(num_validators, len(nodes))

total_stake = sum(validator["stake"] for validator in nodes)
if total_stake == 0:
raise NoValidatorsAvailableError(
"Cannot select validators: all validators have zero stake."
)
probabilities = [validator["stake"] / total_stake for validator in nodes]

selected_validators = rng.choice(
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13 changes: 13 additions & 0 deletions tests/unit/test_vrf.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
import pytest
from backend.consensus.vrf import get_validators_for_transaction
from backend.consensus.base import NoValidatorsAvailableError
from unittest.mock import Mock


Expand Down Expand Up @@ -66,3 +68,14 @@ def choice_mock(a, p, size, replace):

rng.choice.assert_called_once()
assert validators == [{"stake": 3}, {"stake": 2}, {"stake": 1}]


def test_get_validators_for_transaction_zero_stake_raises() -> None:
"""
Regression test for #1732: ZeroDivisionError when all validators have stake=0.
get_validators_for_transaction must raise NoValidatorsAvailableError instead of
crashing with ZeroDivisionError.
"""
nodes = [{"stake": 0}, {"stake": 0}, {"stake": 0}]
with pytest.raises(NoValidatorsAvailableError, match="zero stake"):
get_validators_for_transaction(nodes, 2)