It is now possible to test requests (including conditional logic) before sending them out to your clients. Go to the Preview step at the top of your dashboard, click Select Mode in the upper-right corner, and pick Test from the dropdown menu:

Once done, the system will notify you that the test mode is active. You can use this mode to experiment and play — all changes are temporary and will not be saved.
This mode won’t save your responses, won’t notify your clients, and it won’t affect your client’s experience.