@Test
public void testIsMutable() {

    CollectionQueryEngine<Car> queryEngine = new CollectionQueryEngine<Car>();
    queryEngine.init(emptyObjectStore(), queryOptionsWithOnHeapPersistence());
    Assert.assertTrue(queryEngine.isMutable());
    queryEngine.addIndex(createImmutableIndex(), noQueryOptions());
    Assert.assertFalse(queryEngine.isMutable());
}