diff --git a/app/reports.py b/app/reports.py
index 2d7bf93..9ea26b1 100644
--- a/app/reports.py
+++ b/app/reports.py
@@ -6,7 +6,7 @@
 
 from __future__ import annotations
 
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Iterable
 
 from app.data import all_reports
@@ -16,6 +16,14 @@
 _SORTABLE_FIELDS = {"id", "title", "status", "owner", "amount", "created_at"}
 
 
+def _normalize_datetime(value: datetime | None) -> datetime | None:
+    if value is None:
+        return None
+    if value.tzinfo is None:
+        return value.replace(tzinfo=timezone.utc)
+    return value.astimezone(timezone.utc)
+
+
 def query(
     *,
     status: ReportStatus | None = None,
@@ -29,6 +37,9 @@ def query(
     if sort not in _SORTABLE_FIELDS:
         raise ValueError(f"Unsupported sort field: {sort!r}")
 
+    date_from = _normalize_datetime(date_from)
+    date_to = _normalize_datetime(date_to)
+
     rows: Iterable[Report] = all_reports()
 
     if status is not None:
diff --git a/app/test_main.py b/app/test_main.py
new file mode 100644
index 0000000..5ddd99c
--- /dev/null
+++ b/app/test_main.py
@@ -0,0 +1,45 @@
+from fastapi.testclient import TestClient
+
+from app.main import app
+
+
+client = TestClient(app)
+
+
+def test_health_endpoint() -> None:
+    response = client.get("/health")
+    assert response.status_code == 200
+    assert response.json() == {"status": "ok"}
+
+
+def test_reports_endpoint_supports_query_params() -> None:
+    response = client.get(
+        "/reports",
+        params={
+            "status": "approved",
+            "date_from": "2026-01-10T00:00:00Z",
+            "date_to": "2026-03-01T00:00:00Z",
+            "sort": "amount",
+            "descending": "false",
+            "offset": 1,
+            "limit": 3,
+        },
+    )
+    assert response.status_code == 200
+    payload = response.json()
+    assert payload["offset"] == 1
+    assert payload["limit"] == 3
+    assert payload["total"] >= 0
+    assert len(payload["items"]) <= 3
+    assert all(item["status"] == "approved" for item in payload["items"])
+
+
+def test_reports_endpoint_accepts_date_only_strings() -> None:
+    response = client.get(
+        "/reports",
+        params={"date_from": "2026-01-05", "date_to": "2026-01-10", "limit": 1},
+    )
+    assert response.status_code == 200
+    payload = response.json()
+    assert payload["limit"] == 1
+    assert len(payload["items"]) <= 1