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

backend/app/crud.py

@@ -28,8 +28,8 @@ async def get_sessions(
         count_statement = count_statement.where(SleepSession.start_time >= query_from_date)
     if query_to_date:
         count_statement = count_statement.where(SleepSession.start_time <= query_to_date)
-    count_result = await session.exec(count_statement)
-    total = count_result.one() or 0
+    count_result = await session.execute(count_statement)
+    total = count_result.scalar() or 0
 
     statement = select(SleepSession).order_by(SleepSession.start_time.desc())
     if query_from_date:
@@ -38,14 +38,14 @@ async def get_sessions(
         statement = statement.where(SleepSession.start_time <= query_to_date)
     statement = statement.limit(limit)
 
-    result = await session.exec(statement)
-    sessions = result.all()
+    result = await session.execute(statement)
+    sessions = result.scalars().all()
     return list(sessions), total
 
 async def get_active_session(session: AsyncSession) -> Optional[SleepSession]:
     statement = select(SleepSession).where(SleepSession.end_time == None)
-    result = await session.exec(statement)
-    return result.first()
+    result = await session.execute(statement)
+    return result.scalars().first()
 
 async def create_sleep_session(session: AsyncSession, start_time: datetime) -> SleepSession:
     new_session = SleepSession(start_time=start_time)
@@ -58,8 +58,8 @@ async def end_sleep_session(
     session: AsyncSession, session_id: int, end_time: datetime
 ) -> Union[SleepSession, bool, str, None]:
     statement = select(SleepSession).where(SleepSession.id == session_id)
-    result = await session.exec(statement)
-    sleep_session = result.first()
+    result = await session.execute(statement)
+    sleep_session = result.scalars().first()
 
     if not sleep_session:
         return None  # Not found
@@ -83,8 +83,8 @@ async def end_sleep_session(
 
 async def delete_session(session: AsyncSession, session_id: int) -> bool:
     statement = select(SleepSession).where(SleepSession.id == session_id)
-    result = await session.exec(statement)
-    sleep_session = result.first()
+    result = await session.execute(statement)
+    sleep_session = result.scalars().first()
 
     if not sleep_session:
         return False
@@ -97,8 +97,8 @@ async def update_session(
     session: AsyncSession, session_id: int, update_data: dict
 ) -> Optional[SleepSession]:
     statement = select(SleepSession).where(SleepSession.id == session_id)
-    result = await session.exec(statement)
-    sleep_session = result.first()
+    result = await session.execute(statement)
+    sleep_session = result.scalars().first()
 
     if not sleep_session:
         return None
@@ -112,7 +112,6 @@ async def update_session(
     await session.refresh(sleep_session)
     return sleep_session
 
-
 async def get_sleep_counts_by_start_date(
     session: AsyncSession,
     from_date: Optional[datetime] = None,
@@ -135,5 +134,5 @@ async def get_sleep_counts_by_start_date(
     if query_to_date:
         statement = statement.where(SleepSession.start_time <= query_to_date)
 
-    result = await session.exec(statement)
+    result = await session.execute(statement)
     return list(result.all())