Do you understand that there is nothing deterministic in skills and hooks? it is the same text in -> text out.
Skills can include scripts, tools, etc.
The entire point of hooks is deterministic responses to signals from the LLM. You run a function in response to some event and the function is given json data that conforms to a specific schema.
With that said, part of hooks is you can return a json object to the agent which gives it instructions such as stop, continue, etc but those to my understanding are all very explicit constants rather than loosey-goosey prompts you can pass it.
If this person looked into hooks more, they could write a script that would run their project's tests and then tell Claude to stop if tests end via a non-0 exit code.