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ba2278a | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 | import circuit_breaker as cb_module
from circuit_breaker import CircuitBreaker, CircuitOpenError
import pytest
class _FakeClock:
"""Deterministic stand-in for time.monotonic()."""
def __init__(self, start: float = 0.0):
self.now = start
def __call__(self) -> float:
return self.now
def advance(self, seconds: float) -> None:
self.now += seconds
@pytest.fixture
def clock(monkeypatch):
fake = _FakeClock()
monkeypatch.setattr(cb_module.time, "monotonic", fake)
return fake
def test_before_call_is_a_noop_below_the_failure_threshold(clock):
breaker = CircuitBreaker(failure_threshold=3, cooldown_seconds=60)
breaker.record_failure("bing")
breaker.record_failure("bing")
breaker.before_call("bing") # should not raise - only 2 failures so far
def test_before_call_raises_once_threshold_is_reached(clock):
breaker = CircuitBreaker(failure_threshold=3, cooldown_seconds=60)
for _ in range(3):
breaker.record_failure("bing")
with pytest.raises(CircuitOpenError):
breaker.before_call("bing")
def test_record_success_closes_the_circuit(clock):
breaker = CircuitBreaker(failure_threshold=3, cooldown_seconds=60)
for _ in range(3):
breaker.record_failure("bing")
breaker.record_success("bing")
breaker.before_call("bing") # back to closed - should not raise
def test_before_call_allows_a_trial_after_the_cooldown_elapses(clock):
breaker = CircuitBreaker(failure_threshold=3, cooldown_seconds=60)
for _ in range(3):
breaker.record_failure("bing")
clock.advance(61)
breaker.before_call("bing") # cooldown elapsed - half-open, should not raise
def test_a_failed_trial_after_cooldown_reopens_for_another_full_cooldown(clock):
breaker = CircuitBreaker(failure_threshold=3, cooldown_seconds=60)
for _ in range(3):
breaker.record_failure("bing")
clock.advance(61)
breaker.before_call("bing") # half-open trial begins
breaker.record_failure("bing") # ...and it failed
clock.advance(30) # only 30s into the new cooldown
with pytest.raises(CircuitOpenError):
breaker.before_call("bing")
clock.advance(31) # now past the new 60s cooldown
breaker.before_call("bing") # should not raise
def test_keys_are_independent(clock):
breaker = CircuitBreaker(failure_threshold=2, cooldown_seconds=60)
for _ in range(2):
breaker.record_failure("bing")
breaker.before_call("brave") # untouched key - should not raise
with pytest.raises(CircuitOpenError):
breaker.before_call("bing")
def test_circuit_open_error_carries_the_key_and_remaining_seconds(clock):
breaker = CircuitBreaker(failure_threshold=1, cooldown_seconds=60)
breaker.record_failure("bing")
clock.advance(10)
with pytest.raises(CircuitOpenError) as exc_info:
breaker.before_call("bing")
assert exc_info.value.key == "bing"
assert exc_info.value.retry_after == pytest.approx(50, abs=0.01)
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