How to Mock a GraphQL Backend in Python

from dataclasses import dataclass, asdict
from typing import Any, Dict, List


@dataclass
class Product:
    id: int
    name: str
    price: float


@dataclass
class User:
    id: int
    username: str


class MockGraphQLBackend:
    def __init__(self) -> None:
        self.products = [
            Product(id=1, name="Laptop", price=1200.0),
            Product(id=2, name="Mouse", price=25.0),
        ]
        self.users = [
            User(id=1, username="alice"),
            User(id=2, username="bob"),
        ]

    def resolve_product(self, product_id: int) -> Dict[str, Any] | None:
        product = next((p for p in self.products if p.id == product_id), None)
        return asdict(product) if product else None

    def resolve_all_products(self) -> List[Dict[str, Any]]:
        return [asdict(p) for p in self.products]

    def resolve_user(self, user_id: int) -> Dict[str, Any] | None:
        user = next((u for u in self.users if u.id == user_id), None)
        return asdict(user) if user else None


if __name__ == "__main__":
    backend = MockGraphQLBackend()
    print("All products:", backend.resolve_all_products())
    print("Product 1:", backend.resolve_product(1))
    print("User 2:", backend.resolve_user(2))
    print("Missing product:", backend.resolve_product(999))