fix: preserve metrics with atomic persistence

tests/test_reliability_persistence.py

@@ -0,0 +1,99 @@
+import json
+import threading
+from datetime import datetime, timedelta, timezone
+
+import pytest
+
+from dashboard.persistence import (
+    append_daily_jsonl,
+    atomic_write_json,
+    load_jsonl_tail,
+    merge_observation,
+    onchain_refresh_due,
+)
+
+
+def test_atomic_write_json_remains_readable_under_concurrent_writers(tmp_path):
+    path = tmp_path / "cache.json"
+
+    threads = [
+        threading.Thread(target=atomic_write_json, args=(path, {"writer": i, "values": list(range(100))}))
+        for i in range(12)
+    ]
+    for thread in threads:
+        thread.start()
+    for thread in threads:
+        thread.join()
+
+    saved = json.loads(path.read_text())
+    assert saved["writer"] in range(12)
+    assert saved["values"] == list(range(100))
+    assert not list(tmp_path.glob(".cache.json.*.tmp"))
+
+
+def test_append_daily_jsonl_writes_at_most_one_entry_per_utc_day(tmp_path):
+    path = tmp_path / "scores.jsonl"
+    first = {"timestamp": "2026-07-26T01:00:00+00:00", "score": 10}
+    duplicate_day = {"timestamp": "2026-07-26T23:59:00+00:00", "score": 20}
+    next_day = {"timestamp": "2026-07-27T00:01:00+00:00", "score": 30}
+
+    assert append_daily_jsonl(path, first) is True
+    assert append_daily_jsonl(path, duplicate_day) is False
+    assert append_daily_jsonl(path, next_day) is True
+
+    assert load_jsonl_tail(path, limit=90) == [first, next_day]
+
+
+def test_load_jsonl_tail_is_bounded_and_ignores_malformed_lines(tmp_path):
+    path = tmp_path / "scores.jsonl"
+    path.write_text("".join(json.dumps({"n": i}) + "\n" for i in range(200)) + "partial{")
+
+    assert load_jsonl_tail(path, limit=3, chunk_size=64) == [{"n": 197}, {"n": 198}, {"n": 199}]
+
+
+def test_merge_observation_preserves_last_known_good_with_stale_metadata():
+    old = {
+        "value": 1.25,
+        "observed_at": "2026-07-25T12:00:00+00:00",
+        "source": "lookintobitcoin",
+        "stale": False,
+        "last_error": None,
+    }
+
+    merged = merge_observation(old, None, source="lookintobitcoin", error="timeout")
+
+    assert merged == {
+        "value": 1.25,
+        "observed_at": "2026-07-25T12:00:00+00:00",
+        "source": "lookintobitcoin",
+        "stale": True,
+        "last_error": "timeout",
+    }
+
+
+def test_merge_observation_records_metadata_for_fresh_value():
+    observed_at = "2026-07-26T12:00:00+00:00"
+
+    merged = merge_observation(
+        {"value": 1.0}, {"value": 2.0, "trend": "up"},
+        source="checkonchain", observed_at=observed_at,
+    )
+
+    assert merged["value"] == 2.0
+    assert merged["trend"] == "up"
+    assert merged["observed_at"] == observed_at
+    assert merged["source"] == "checkonchain"
+    assert merged["stale"] is False
+    assert merged["last_error"] is None
+
+
+@pytest.mark.parametrize("timestamp", [None, "", "not-a-time"])
+def test_onchain_refresh_due_when_timestamp_is_missing_or_invalid(timestamp):
+    assert onchain_refresh_due(timestamp, now=datetime(2026, 7, 26, tzinfo=timezone.utc)) is True
+
+
+def test_onchain_refresh_due_after_ttl():
+    now = datetime(2026, 7, 26, 12, tzinfo=timezone.utc)
+
+    assert onchain_refresh_due((now - timedelta(hours=5)).isoformat(), now=now, ttl_seconds=21600) is False
+    assert onchain_refresh_due((now - timedelta(hours=7)).isoformat(), now=now, ttl_seconds=21600) is True