Simplify your Python tests with dirty equals

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Imagine this scenario, you have created a Todo API and you return this payload when requesting a single todo.

{
    "created_at": "2023-08-27T17:31:14.355813",
    "done": False,
    "id": "70592516-24d5-4582-8d80-54b2c70b5ab1",
    "metadata": {
        "foo": "bar",
        "text": "bla bla"
    },
    "name": "Learn Python",
    "updated_at": None
}

How will you test this payload? Especially the datetime and uuid objects.

For the uuid, my strategy was to use a unittest mock utility or to write a function testing if I could get a uuid.UUID object and returns a boolean.

For the datetime, I use freezegun to freeze the date to a particular value. You can also use another package like time-machine (discovered recently). Thus I ended up with a test code like the following:

import uuid

from fastapi.testclient import TestClient
from freezegun import freeze_time

from api import app

client = TestClient(app)


def is_uuid(value: str) -> bool:
    try:
        uuid.UUID(value)
        return True
    except ValueError:
        return False


@freeze_time('2023-08-27 18:00')
def test_get_todo():
    response = client.get('/')
    assert response.status_code == 200
    data = response.json()

    assert is_uuid(data['id'])
    assert data['created_at'] ==…