@Marvin I tried to use prefect_test_harness but get error sqlite3.OperationalError: unable to open database file

Ah, the joys of database errors. Let's track down the cause and solution. We can start by searching the Prefect documentation and GitHub issues for insights on

prefect_test_harness

and the specific error you're encountering. I'll look into: 1. Any mentions of

prefect_test_harness

in the Prefect docs. 2. Any GitHub issues related to

prefect_test_harness

and

sqlite3.OperationalError

. Give me a moment. It looks like there are a couple of useful pieces of information. ### Documentation Insights The Prefect documentation mentions using

prefect_test_harness

to run flows and tasks against a temporary local SQLite database. Here’s a simplified example:

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():
        assert my_favorite_flow() == 42

Refer to the Prefect Testing Guide for more details. ### GitHub Issues Related 1. sqlite3.OperationalError and Skipped Unsupported Reflection: - Example scenarios indicate that the temporary databases used within

prefect_test_harness

may not have all the required schema depending on the test scope. This could be a factor in the database not opening correctly. - GitHub Issue #14483 indicates there were reflection issues with some table schemas. 2. Schema Incompleteness: - Another issue reported, #6660, indicates that

prefect_test_harness

may not contain the entire schema for testing operations beyond basic flow executions. ### Actions You Can Take 1. Inspect and Reset Database: - Ensure your SQLite database is set up correctly and reset it if needed using the CLI command:

prefect server database reset -y

2. Use Fixtures Appropriately: - If you are using test fixtures, ensure they are scoped correctly to avoid excessive overhead and database locks. 3. Manual Schema Configuration: - For more complex tests needing certain tables (like

block_schema

), you may need to configure the database schema manually during the test setup. For further assistance, refer to the respective GitHub issues and documentation links provided or raise a new issue if your problem persists. Good luck. Sigh, I suppose someone has to do the joyful job of error fixing. Links: - Prefect Testing Guide - GitHub Issue #14483 - GitHub Issue #6660