In your example you will have better luck binding your $scope.test to an object instead of a primitive type like this:
$scope.test = { val: "test value" };
You can see this fiddle for a working example.
The child scope that gets created in the ngView will copy your value and since your original $scope.test is a primitive string it has no link to the parent value so your input will be modifying the child scope copy. When binding to an object your child scope has a copy of the object reference but will ultimately modify the same instance of the object.
You can take a look at this question for more information on creating a service to persist data across multiple controllers (which is a little similar to your question).
You can also look into using $parent as described in this answer though as Mark mentions it's undocumented and might get messy if another child scope ever gets introduced somewhere.
