Cover fail-closed timestamp validation

backend/services/infonet/tests/test_time_validity_invalid_timestamps.py

@@ -1,13 +1,15 @@
 """Regression coverage for malformed chain timestamps."""
 
+from typing import Any
+
 from services.infonet.time_validity import chain_majority_time, is_event_too_future
 
 
-def _event(node_id: str, timestamp):
+def _event(node_id: str, timestamp: Any) -> dict[str, Any]:
     return {"node_id": node_id, "timestamp": timestamp}
 
 
-def test_chain_majority_time_ignores_malformed_and_nonfinite_timestamps():
+def test_chain_majority_time_ignores_malformed_and_nonfinite_timestamps() -> None:
     chain = [
         _event("valid-a", 10.0),
         _event("bad-text", "not-a-timestamp"),
@@ -19,12 +21,18 @@ def test_chain_majority_time_ignores_malformed_and_nonfinite_timestamps():
     assert chain_majority_time(chain) == 15.0
 
 
-def test_chain_majority_time_accepts_finite_numeric_strings():
+def test_chain_majority_time_accepts_finite_numeric_strings() -> None:
     chain = [_event("a", "10.5"), _event("b", "20.5")]
 
     assert chain_majority_time(chain) == 15.5
 
 
-def test_future_check_does_not_treat_nonfinite_timestamp_as_valid():
-    assert not is_event_too_future(_event("a", float("nan")), chain_time=100.0)
-    assert not is_event_too_future(_event("a", float("inf")), chain_time=100.0)
+def test_future_check_fails_closed_for_invalid_timestamps() -> None:
+    assert is_event_too_future(_event("bad-text", "not-a-timestamp"), chain_time=100.0)
+    assert is_event_too_future(_event("bad-nan", float("nan")), chain_time=100.0)
+    assert is_event_too_future(_event("bad-inf", float("inf")), chain_time=100.0)
+
+
+def test_future_check_preserves_valid_timestamp_behavior() -> None:
+    assert not is_event_too_future(_event("near", 110.0), chain_time=100.0)
+    assert is_event_too_future(_event("far", 10_000.0), chain_time=100.0)