To my understanding all you have given to test2 as test1 is 'CREATE USER' sytem privilege. until you grant the object privileges of test1, test2 can't see the contents/objects of test2.

Take practical example in day to day life at work, system user will not be having object privileges of schema/application owner unless otherwise you give explicitely...

So, test1,test2 setup also works the same way. You are talking about only system privileges, you forgot here object privileges. If you have enterprise manager go and see how the privileges set up for those 2 users you have created. Otherwise try to query the privileges of test1 and test2 and see, you get the clear picture. Correct me If Iam wrong...