### Question:
ObjectVertex implements Vertex { @Override public <V> VertexProperty<V> property(VertexProperty.Cardinality cardinality, String key, V value, Object... keyValues) { throw new UnsupportedOperationException("Adding properties not supported"); } private  ObjectVertex(ActGraph graph,
                       ObjectRecord object,
                       ObjectFactTypeResolver.ObjectTypeStruct type,
                       List<PropertyEntry<?>> properties); @Override Edge addEdge(String label, Vertex inVertex, Object... keyValues); @Override Iterator<Edge> edges(Direction direction, String... edgeLabels); @Override Iterator<Vertex> vertices(Direction direction, String... edgeLabels); @Override Iterator<VertexProperty<V>> properties(String... propertyKeys); @Override VertexProperty<V> property(VertexProperty.Cardinality cardinality, String key, V value, Object... keyValues); @Override Object id(); @Override String label(); @Override Graph graph(); @Override void remove(); ObjectRecord getObjectRecord(); static Builder builder(); @Override String toString(); @Override boolean equals(Object o); @Override int hashCode();  }### Answer:
@Test public void testReturnEmptyPropertyIfKeyNonExistent() { Vertex vertex = createVertex(); VertexProperty property = vertex.property("something"); assertEquals(VertexProperty.empty(), property); }