When testing NAT directly on a Juniper (SRX). How to do ping from source?

On a Cisco you can simply ping out using the source IP of the LAN and it will trigger NAT. This is good for testing NAT works as well as testing things like VPN's.

When doing the same thing on a Juniper SRX it doesn't seem to trigger NAT when doing it from the Juniper itself. Is there an easy way to do this?

Thanks