The new (1.0.52) rule editor allows you to create your own rules. It needs work, but basically you should set the name as something like player_test. Set the source to player and target as test. Next, edit any of the available entities to the test collection. Note that at least currently there is no way to have entities in multiple collections. This is because, ultimately, each entity is checked for damage allow/deny at run time and in comparison to active rules in a ruleset. It might get a little messy if an entity were to be compared to multiple rules.