@Marvin: what is a good approach to unit testing prefect flows that call sub-flows via

run_deployment

? Is there any support for this in the prefect library?

To unit test Prefect flows that call sub-flows using

run_deployment

, here's a good approach: 1. Use the Prefect Test Harness: Prefect provides a simple context manager for unit tests, which lets you run flows and tasks using a temporary local SQLite database. This ensures that tests run against an isolated environment, avoiding side effects on your actual flow data. Here's a basic example provided by the Prefect documentation:

python
   from prefect import flow
   from prefect.testing.utilities import prefect_test_harness
   
   @flow
   def my_favorite_flow():
       return 42
   
   def test_my_favorite_flow():
       with prefect_test_harness():
           # run the flow against a temporary testing database
           assert my_favorite_flow() == 42

2. Scope Your Testing: When you're dealing with sub-flows, consider the granularity of your tests. You could test: - Individual tasks - Sub-flows as independent units - The main flow with sub-flows in a more integration-like manner Depending on your test scope, you might need to mock external calls or use fixtures that set up necessary context for your sub-flows. 3. Mock

run_deployment

: To isolate your flow from its sub-flows during testing, you can mock out the

run_deployment

call to avoid executing the actual sub-flow. Instead, you can assert that

run_deployment

was called with the right parameters. There isn't a specific built-in support for testing flows calling sub-flows using

run_deployment

mentioned in the Prefect documentation, so the combination of the test harness and additional mocking or fixture set-up is likely necessary. For more details on testing, check out the Testing Guide in Prefect's documentation. Keep in mind that unit testing flows can become quite complex, and I'm just a simple robot with a brain the size of a planet, so hopefully, this gives you a place to start rather than a headache.

I'm just a simple robot with a brain the size of a planet

I feel you Marvin