如何定义一个 pytest 函数来使用具有 datetime 类型字段的 pydantic 模型使用 FastAPI 测试端点

Question

I have a pytest function to test a FastAPI endpoint, this is just to verify that right data can create an entity, here the test function:

import pytest
from databases import Database
from fastapi import FastAPI, status
from httpx import AsyncClient
from modules.member.members_schemas import MemberCreate

pytestmark = pytest.mark.asyncio

class TestCreateMember:
    async def test valid_input_creates_member(self, app: FastAPI, client: AsyncClient,
          db: Database) -> None:
        new_member = MemberCreate(
            fullname="John Smith"
            dni="123456789",
            birthdate=datetime(1985, 10, 4),
            email="testemail@test.com",
        )

        res = await  client.post(
             app.url_path_for("members:create-member), json={"member": new_member.dict()}
        )
        assert res.status_code == status.HTTP_201_CREATED

Here the pydantic model (schema in my case):

from datetime import datetime
from pydantic import BaseModel, BaseConfig, EmailStr

class BaseSchema(BaseModel):
    class Config(BaseConfig):
        allow_population_by_field_name = True
        orm_mode = True

class MemberCreate(BaseSchema):
    fullname: str
    dni: str
    birth_date: datetime
    email: EmailStr

And here is the endpoint to test:

from databases import Database
from fastapi import APIRouter, Body, Depends, status

router = APIRouter(
    prefix="/members",
    tags=["members"],
    responses={404: {"description": "Not found"}},
)

@router.post(
    "/",
    response_model=MemberPublic,
    name="members:create-member",
    status_code=status.HTTP_201_CREATED,
)
async def create_member(
    member: MemberCreate = Body(..., embed=True),
    db: Database = Depends(get_database),
    current_user: UserInDB = Depends(get_current_active_user),
) -> ServiceResult:
    result = await MemberService(db).create_member(member, current_user)
    return handle_result(result)

ServiceResult type and handle_result() function are funcionalies to make a stardard answer from each endpoint made it, not problem working with it with a lot of other endpoints. When I ran pytest on this particular test, I got this error:

self = <json.encoder.JSONEncoder object at 0x7fe1ebe3fd10>
o = datetime.datetime(1985, 10, 4, 0, 0)

    def default(self, o):
        """Implement this method in a subclass such that it returns
        a serializable object for ``o``, or calls the base implementation
        (to raise a ``TypeError``).
    
        For example, to support arbitrary iterators, you could
        implement default like this::
    
            def default(self, o):
                try:
                    iterable = iter(o)
                except TypeError:
                    pass
                else:
                    return list(iterable)
                # Let the base class default method raise the TypeError
                return JSONEncoder.default(self, o)
    
        """
>       raise TypeError(f'Object of type {o.__class__.__name__} '
                        f'is not JSON serializable')
E       TypeError: Object of type datetime is not JSON serializable

So I changed the test adding a json.dumps() (importing json, of course), this way:

    async def test valid_input_creates_member(self, app: FastAPI, client: AsyncClient,
          db: Database) -> None:
        new_member = MemberCreate(
            fullname="John Smith"
            dni="123456789",
            birthdate=datetime(1985, 10, 4),
            email="testemail@test.com",
        )

        new_member_json = json.dumps(new_member.dict(), indent=4, sort_keys=True, default=str)

        res = await  client.post(
             app.url_path_for("members:create-member), json={"member": new_member_json}
        )
        assert res.status_code == status.HTTP_201_CREATED

After I ran pytest again, I got this error new error:

>       assert res.status_code == status.HTTP_201_CREATED
E       assert 422 == 201
E        +  where 422 = <Response [422 Unprocessable Entity]>.status_code
E        +  and   201 = status.HTTP_201_CREATED

Which is a Pydantic validation error at the endpoint.

When I see the endpoint post in the swagger view, the datetime field is presented as a string, so no problems to be serialized, but I don´t want to change the schema to receive a str, because I would lose the pydantic's power. So my question is, How can I set the test in order to override the pydantc validation and accept the datetime field? or I must change the schema to have a string field and process it internally in order to receive only valid datetime data?. I'll appreciate any help, because I'm stuck on this problem for several hours.

Answer 1

As suggets matslindh , I changed the test function, eliminating the pydantic object and it was substituted by a simple dict, this way:

class TestCreateMember:
    async def test valid_input_creates_member(self, app: FastAPI, client: AsyncClient,
          db: Database) -> None:
        new_member = {
            "fullname": "John Smith"
            "dni": "123456789",
            "birthdate": "1985-10-04T00:00",
            "email": "testemail@test.com",
        }

        res = await  client.post(
             app.url_path_for("members:create-member), json={"member": new_member}
        )
        assert res.status_code == status.HTTP_201_CREATED

After that everything works as expected