[Python] How can I mock my environment variables for my pytest?

I've looked at some examples to mock environment variables. Here

In my case, I have to mock a variable in my config.py file that is setup as follows:

class ServiceConfig(BaseSettings):
...
API_AUDIENCE: str = os.environ.get("API_AUDIENCE")
...
...



I have that called here:

class Config(BaseSettings):
auth: ClassVar[ServiceConfig] = ServiceConfig()


I've attempted to patch that value as follows:

@mock.patch.dict(os.environ, {"API_AUDIENCE": "https://mock.com"})
class Test(TestCase):


Another way I've tried is:

@patch('config.Config.API_AUDIENCE', "https://mock.com")
def ....:


The setup is incorrect both ways, getting this error:

E pydantic_core._pydantic_core.ValidationError: 1 validation error for
ServiceConfig
E API_AUDIENCE


What is the correct way to setup mocking an environment variable?

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