type chattyPrinter struct {
	w          io.Writer
	lastNameMu sync.Mutex // guards lastName
	lastName   string     // last printed test name in chatty mode
	json       bool       // -v=json output mode
}

func newChattyPrinter(w io.Writer) *chattyPrinter {
	return &chattyPrinter{w: w, json: chatty.json}
}

// prefix is like chatty.prefix but using p.json instead of chatty.json.