prefect_test_harness fixture doesn't work when used under unittest.IsolatedAsyncioTestCase

[ori-scala]

Bug summary

When trying to use the harness fixture in combination with unittest.IsolatedAsyncioTestCase, the local server isn't recognized when trying to get it using get_client.

Minimal reproducible example: Note that you should make sure that you're logged out and not using an ephemeral server

prefect cloud logout
prefect config set PREFECT_SERVER_ALLOW_EPHEMERAL_MODE='False'

import unittest

from prefect import flow
import pytest
from prefect.client.orchestration import get_client
from prefect.testing.utilities import prefect_test_harness


@pytest.fixture(autouse=True, scope="session")
def prefect_test_fixture():
    with prefect_test_harness():
        yield


@flow
def my_favorite_flow():
    return 42


# PASS
def test_my_favorite_flow():
    client = get_client()
    print(f"client: {client.api_url}")
    assert my_favorite_flow() == 42


# PASS
class SyncTestCase(unittest.TestCase):
    def test_my_favorite_flow(self):
        client = get_client()
        print(f"client: {client.api_url}")
        assert my_favorite_flow() == 42


# FAIL! see the error below
class AsyncTestCase(unittest.IsolatedAsyncioTestCase):
    def test_my_favorite_flow(self):
        client = get_client()
        print(f"client: {client.api_url}")
        assert my_favorite_flow() == 42


# PASS
class AsyncTestCase2(unittest.IsolatedAsyncioTestCase):
    def test_my_favorite_flow(self):
        with prefect_test_harness():
            client = get_client()
            print(f"client: {client.api_url}")
            assert my_favorite_flow() == 42

Error is:

        if not api and PREFECT_SERVER_ALLOW_EPHEMERAL_MODE:
            # create an ephemeral API if none was provided
            from prefect.server.api.server import SubprocessASGIServer
    
            server = SubprocessASGIServer()
            server.start()
            assert server.server_process is not None, "Server process did not start"
    
            api = server.api_url
            server_type = ServerType.EPHEMERAL
        elif not api and not PREFECT_SERVER_ALLOW_EPHEMERAL_MODE:
>           raise ValueError(
                "No Prefect API URL provided. Please set PREFECT_API_URL to the address of a running Prefect server."
            )
E           ValueError: No Prefect API URL provided. Please set PREFECT_API_URL to the address of a running Prefect server.

Version info

Version:             3.0.10
API version:         0.8.4
Python version:      3.12.3
Git commit:          3aa2d893
Built:               Tue, Oct 15, 2024 1:31 PM
OS/Arch:             darwin/x86_64
Profile:             default
Server type:         unconfigured
Pydantic version:    2.9.2

Additional context

No response