Add risk management features: implement KillSwitch and StopConditionsGuard; update settings and tests

tests/unit/test_stop_conditions.py

@@ -0,0 +1,57 @@
+from __future__ import annotations
+
+import pytest
+
+from arbitrade.risk.stop_conditions import StopConditionsGuard
+
+
+def test_stop_conditions_guard_halts_on_source_latency_breach() -> None:
+    guard = StopConditionsGuard(max_source_latency_ms=50.0)
+
+    guard.observe_latency(source_latency_ms=75.0, apply_latency_ms=1.0)
+
+    assert guard.is_halted
+    assert guard.halted_reason == "source_latency_limit_breached"
+
+
+def test_stop_conditions_guard_halts_on_apply_latency_breach() -> None:
+    guard = StopConditionsGuard(max_apply_latency_ms=2.0)
+
+    guard.observe_latency(source_latency_ms=None, apply_latency_ms=3.5)
+
+    assert guard.is_halted
+    assert guard.halted_reason == "apply_latency_limit_breached"
+
+
+def test_stop_conditions_guard_halts_on_consecutive_failures() -> None:
+    guard = StopConditionsGuard(max_consecutive_failures=2)
+
+    guard.register_failure()
+    assert not guard.is_halted
+
+    guard.register_failure()
+
+    assert guard.is_halted
+    assert guard.halted_reason == "consecutive_failures_limit_breached"
+
+
+def test_stop_conditions_guard_resets_failures_after_success() -> None:
+    guard = StopConditionsGuard(max_consecutive_failures=3)
+
+    guard.register_failure()
+    guard.register_success()
+    guard.register_failure()
+
+    assert guard.consecutive_failures == 1
+    assert not guard.is_halted
+
+
+def test_stop_conditions_guard_rejects_invalid_configuration() -> None:
+    with pytest.raises(ValueError, match="max_source_latency_ms"):
+        StopConditionsGuard(max_source_latency_ms=0.0)
+
+    with pytest.raises(ValueError, match="max_apply_latency_ms"):
+        StopConditionsGuard(max_apply_latency_ms=-1.0)
+
+    with pytest.raises(ValueError, match="max_consecutive_failures"):
+        StopConditionsGuard(max_consecutive_failures=0)