I apologize, but it seems my initial search did not return relevant information about changing the state of a particular task using Prefect CLI for the purpose of testing an on-failure hook. I will conduct another search to try to find more specific details on this topic. Please give me a moment.
The search results indicate that you can manually apply any state to a task, which suggests that it is possible to change the state of a particular task for testing purposes. However, the specifics of how to do this via the Prefect CLI are not explicitly detailed in the excerpts provided.
From what I can gather, if the functionality to change the state of a task through Prefect CLI exists, it might be part of the overall orchestration rules or the workflow engine. It was mentioned that users can always apply any state manually, which could imply using the Prefect UI or possibly the CLI.
Since the exact method to do this via the Prefect CLI was not found, I would recommend looking directly at the Prefect documentation or community resources for detailed instructions.
If Prefect CLI does not support this directly, you might consider using the Python client library to set the state programmatically, which could then trigger the on-failure hook as part of your testing. If you need further assistance, please let me know.