test: upgrade backend test suite, implement unit tests, and modernize CRUD patterns

backend/tests/test_bug_repro.py

@@ -1,4 +1,35 @@
 import pytest
+from datetime import datetime, timedelta, timezone
+from app.models import SleepSession
+from sqlalchemy import select
+
+@pytest.mark.asyncio
+async def test_summary_double_counting_midnight(api_client, db_session):
+    # 1. Setup: Insert a sleep session that spans across midnight
+    start_time = datetime(2024, 1, 1, 23, 0)
+    end_time = datetime(2024, 1, 2, 7, 0)
+    
+    new_session = SleepSession(start_time=start_time, end_time=end_time)
+    db_session.add(new_session)
+    await db_session.commit()
+
+    # 2. Call the stats endpoint for a period that includes this session
+    from_date = "2024-01-01T00:00:00"
+    to_date = "2024-01-02T23:59:59"
+    
+    async with api_client as ac:
+        response = await ac.get(f"/api/stats/summary?from_date={from_date}&to_date={to_date}")
+    
+    assert response.status_code == 200
+    data = response.json()
+    
+    # 3. Verify that total_sleeps is exactly 1 for the requested period
+    print(f"DEBUG: data={data}")
+    assert data["total_sleeps"] == 1, f"Expected 1 sleep session, got {data['total_sleeps']}"
+    
+    # 4. Verify that all-time stats also count this session exactly once
+    assert data["total_sleeps_all_time"] == 1, f"Expected 1 all-time sleep session, got {data['total_sleeps_all_time']}"
+
 from datetime import datetime, timedelta, timezone
 from app.models import SleepSession
 from sqlmodel.ext.asyncio.session import AsyncSession