Add comprehensive test suite and utilities for user functionality

This commit introduces a suite of tests for user models, schemas, CRUD operations, and authentication services. It also adds utilities for in-memory database setup to support these tests and updates environment settings for consistency.

backend/app/utils/test_utils.py

@@ -0,0 +1,79 @@
+import logging
+from sqlalchemy import create_engine, event
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
+from sqlalchemy.orm import sessionmaker, clear_mappers
+from sqlalchemy.pool import StaticPool
+
+from app.core.database import Base
+
+logger = logging.getLogger(__name__)
+
+def get_test_engine():
+    """Create an SQLite in-memory engine specifically for testing"""
+    test_engine = create_engine(
+        "sqlite:///:memory:",
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,  # Use static pool for in-memory testing
+        echo=False
+    )
+
+    return test_engine
+
+def setup_test_db():
+    """Create a test database and session factory"""
+    # Create a new engine for this test run
+    test_engine = get_test_engine()
+
+    # Create tables
+    Base.metadata.create_all(test_engine)
+
+    # Create session factory
+    TestingSessionLocal = sessionmaker(
+        autocommit=False,
+        autoflush=False,
+        bind=test_engine,
+        expire_on_commit=False
+    )
+
+    return test_engine, TestingSessionLocal
+
+def teardown_test_db(engine):
+    """Clean up after tests"""
+    # Drop all tables
+    Base.metadata.drop_all(engine)
+
+    # Dispose of engine
+    engine.dispose()
+
+async def get_async_test_engine():
+    """Create an async SQLite in-memory engine specifically for testing"""
+    test_engine = create_async_engine(
+        "sqlite+aiosqlite:///:memory:",
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,  # Use static pool for in-memory testing
+        echo=False
+    )
+    return test_engine
+
+
+async def setup_async_test_db():
+    """Create an async test database and session factory"""
+    test_engine = await get_async_test_engine()
+
+    async with test_engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+
+    AsyncTestingSessionLocal = sessionmaker(
+        autocommit=False,
+        autoflush=False,
+        bind=test_engine,
+        expire_on_commit=False,
+        class_=AsyncSession
+    )
+
+    return test_engine, AsyncTestingSessionLocal
+
+
+async def teardown_async_test_db(engine):
+    """Clean up after async tests"""
+    await engine.dispose()