A member in a clan can battle another member in his clan during preparation day, (no loot will be lost and no trophy deduction).

If for example John battles Jack

he clicks the clan castle,
then clicks on a member,
then he clicks 'BATTLE'

And It begins

Just like a normal battle

. After the simultation battle, it will be automatically be posted on clan chat tab for all to see.
In order to avoid spamming you get a cooldown after a simultation battle.

This feature should be added just for the fun of battling your clan member and also for people to know the strenght and weakness in their base layout before you its war day.