How to Query Multiple Child Objects in Single Query

Test 3 is Parent,Test1 and Test 2 have Lookup relation to Test 3

[select id,name,(select id,name from test1s__r),(select id,name from test2s__r) from test3__c]

 Standard Object As Example:

SELECT id,(SELECT Id,Status,CaseNumber FROM Cases),(SELECT Id,Name FROM Contacts) FROM Account