@Marvin Is there a way to apply mocks from pytest fixtures to flows being run inside a prefect test harness?

Yes, you can apply mocks from pytest fixtures to flows being run inside a Prefect test harness. The

prefect_test_harness

utility is designed to create a temporary testing environment, allowing you to run Prefect flows and tasks in isolation. Here is a basic example of how you might use pytest fixtures with Prefect: 1. Setup a pytest fixture using `prefect_test_harness`:

python
   import pytest
   from prefect.testing.utilities import prefect_test_harness

   @pytest.fixture(autouse=True)
   def prefect_db():
       with prefect_test_harness() as harness:
           yield harness

2. Mocking in your tests: You can use Python's

unittest.mock

library to mock components within your flows or tasks. Here's an example of mocking a task:

python
   from unittest.mock import patch
   from prefect import task, flow

   @task
   def some_task():
       return "real result"

   @flow
   def some_flow():
       return some_task()

   def test_some_flow():
       with patch('path.to.some_task') as mock_task:
           mock_task.return_value = "mocked result"
           result = some_flow()
           assert result == "mocked result"

3. Handling known issues: Be aware of issues such as

MissingContextError

when using

get_run_logger()

outside of an active flow or task context. This error can occur if you try to access the logger in a test without a proper Prefect context. You can avoid this by not using

get_run_logger()

directly in tests or by ensuring the context is correctly set up. For more detailed examples and understanding, you can refer to these resources: - Prefect Test Harness Example - GitHub Issue on MissingContextError If you have any specific requirements or issues, feel free to share more details.