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/tests/conftest.py

@@ -0,0 +1,66 @@
+# tests/conftest.py
+import uuid
+from datetime import datetime, timezone
+
+import pytest
+
+from app.models.user import User
+from app.utils.test_utils import setup_test_db, teardown_test_db, setup_async_test_db, teardown_async_test_db
+
+
+@pytest.fixture(scope="function")
+def db_session():
+    """
+    Creates a fresh SQLite in-memory database for each test function.
+    
+    Yields a SQLAlchemy session that can be used for testing.
+    """
+    # Set up the database
+    test_engine, TestingSessionLocal = setup_test_db()
+
+    # Create a session
+    with TestingSessionLocal() as session:
+        yield session
+
+    # Clean up
+    teardown_test_db(test_engine)
+
+
+@pytest.fixture(scope="function")  # Define a fixture
+async def async_test_db():
+    """Fixture provides new testing engine and session for each test run to improve isolation."""
+
+    test_engine, AsyncTestingSessionLocal = await setup_async_test_db()
+    yield test_engine, AsyncTestingSessionLocal
+    await teardown_async_test_db(test_engine)
+
+@pytest.fixture
+def user_create_data():
+    return {
+        "email": "newtest@example.com",  # Changed to avoid conflict with mock_user
+        "password": "TestPassword123!",
+        "first_name": "Test",
+        "last_name": "User",
+        "phone_number": "+1234567890",
+        "is_superuser": False,
+        "preferences": None
+    }
+
+
+@pytest.fixture
+def mock_user(db_session):
+    """Fixture to create and return a mock User instance."""
+    mock_user = User(
+        id=uuid.uuid4(),
+        email="mockuser@example.com",
+        password_hash="mockhashedpassword",
+        first_name="Mock",
+        last_name="User",
+        phone_number="1234567890",
+        is_active=True,
+        is_superuser=False,
+        preferences=None,
+    )
+    db_session.add(mock_user)
+    db_session.commit()
+    return mock_user