How to validate a Json file in python without using raises?

Question

I have been writing a testcase using pytest concerning a flask config file (flask.config.from_file) in which the file must be Json.

So I did this:

import pytest
from json import load as json_load

def test_config_file(app_client, config_client):
    config_file= "./files/config.json"
    app_client(config_file=config_file)
    config_client.from_file(config_file ,load=json_load)
    with open("/home/shayan/trystack/trystack/files/config.json", "r") as file:  
        config_dict = json_load(file)
        assert config_file.endswith(".json") == True

BTW, I am a junior developer :)

here is my conftest.py:

@pytest.fixture
def app():
    return create_app()
@pytest.fixture
def config_client(app):
    return app.config
@pytest.fixture
def app_client():
    return create_app

create_app gets config_file as an argument in my main module.

I want to check if config_file is Json or not. I have already checked the extension of config_file but what is the best-practice for checking the actual file being Json?

There is already a question about validating using raises but I am looking for other ones if possible.