public static Zoo filledZoo()
    {
        Zoo zoo = new Zoo();

        Elephant elephant = filledElephant();
        Bear bear = filledBear();
        Tiger tiger = filledTiger();

        zoo.largestAnimal = elephant;

        zoo.animals.add(bear);
        zoo.animals.add(tiger);
        zoo.animals.add(elephant);

        return zoo;
    }
Test for polymorphic serialization.
<p>
See {@link RuntimeDerivativeField} for details.

@author David Yu
@created Jan 15, 2011
protostuff-runtime/src/test/java/io/protostuff/runtime/PolymorphicSerializationTest.java