Add tests for auth dependencies and security utilities

Introduced unit tests for `get_current_user`, `get_current_active_user`, and security functions like token creation and decoding. Also refactored imports for consistency and cleaned up unused or misplaced code to improve maintainability.

backend/tests/auth/dependencies.py

@@ -0,0 +1,75 @@
+from unittest.mock import AsyncMock
+
+import pytest
+from fastapi import HTTPException
+from jose import jwt
+
+from app.auth.dependencies import get_current_user, get_current_active_user
+from app.auth.security import SECRET_KEY, ALGORITHM
+from app.models.user import User
+
+
+@pytest.fixture
+def mock_user():
+    return User(
+        id="123e4567-e89b-12d3-a456-426614174000",
+        email="test@example.com",
+        password_hash="hashedpassword",
+        is_active=True
+    )
+
+
+@pytest.mark.asyncio
+async def test_get_current_user_success(mock_user):
+    valid_token = jwt.encode({"sub": str(mock_user.id), "type": "access"}, SECRET_KEY, algorithm=ALGORITHM)
+
+    mock_db = AsyncMock()
+    mock_db.get.return_value = mock_user
+
+    user = await get_current_user(token=valid_token, db=mock_db)
+    assert user == mock_user
+    mock_db.get.assert_called_once_with(User, mock_user.id)
+
+
+@pytest.mark.asyncio
+async def test_get_current_user_invalid_token():
+    invalid_token = "invalid.token.payload"
+
+    with pytest.raises(HTTPException) as exc_info:
+        await get_current_user(token=invalid_token, db=AsyncMock())
+
+    assert exc_info.value.status_code == 401
+    assert exc_info.value.detail == "Could not validate credentials"
+
+
+@pytest.mark.asyncio
+async def test_get_current_user_wrong_token_type():
+    token = jwt.encode({"sub": "123", "type": "refresh"}, SECRET_KEY, algorithm=ALGORITHM)
+
+    with pytest.raises(HTTPException) as exc_info:
+        await get_current_user(token=token, db=AsyncMock())
+
+    assert exc_info.value.status_code == 401
+    assert exc_info.value.detail == "Could not validate credentials"
+
+
+@pytest.mark.asyncio
+async def test_get_current_active_user_success(mock_user):
+    result = await get_current_active_user(mock_user)
+    assert result == mock_user
+
+
+@pytest.mark.asyncio
+async def test_get_current_active_user_inactive():
+    inactive_user = User(
+        id="123e4567-e89b-12d3-a456-426614174000",
+        email="inactive@example.com",
+        password_hash="hashedpassword",
+        is_active=False
+    )
+
+    with pytest.raises(HTTPException) as exc_info:
+        await get_current_active_user(inactive_user)
+
+    assert exc_info.value.status_code == 400
+    assert exc_info.value.detail == "Inactive user"