@Marvin When I use contextmanager

prefect_test_harness

with Prefect 2 for unit tests with Pytest, I have this error: sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) unable to open database file

The error you're experiencing,

sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) unable to open database file

, when using

prefect_test_harness

in Prefect 2 with Pytest could be due to several reasons related to the SQLite database setup for testing. ### Possible Causes and Solutions: 1. Database Path Issue: Ensure that the path to the SQLite database is correctly set and that the directory exists. The

prefect_test_harness

context manager uses a temporary SQLite database, and any issues with file paths can lead to this error. 2. Permissions: Check if the directory where the SQLite database is being created has the appropriate read/write permissions. 3. Concurrent Access: If multiple tests are trying to access the database simultaneously, it might cause conflicts. Make sure the tests are not running in parallel unless you have configured the database to handle such access. 4. Fixture Setup: If you're using

prefect_test_harness

as a fixture in Pytest, ensure that it's correctly set up to manage the database lifecycle, i.e., creation and teardown. 5. Schema Issues: There are known issues where

prefect_test_harness

might not contain the entire schema needed for some operations. If your tests involve complex database interactions, ensure the necessary tables and schema are set up. ### References: - Prefect Testing Guide - Prefect GitHub Issue on `prefect_test_harness` - Discusses schema issues with

prefect_test_harness

. If these suggestions don't resolve your issue, you may want to provide more context or consider opening an issue on Prefect's GitHub repository for more specific guidance.