@Test
    @FeatureRequirementSet(FeatureRequirementSet.Package.VERTICES_ONLY)
    public void shouldNotConstructNewWithSomethingAlreadyDetached() {
        final Vertex v = graph.addVertex();
        final ReferenceVertex referenceVertex = ReferenceFactory.detach(v);
        assertSame(referenceVertex, ReferenceFactory.detach(referenceVertex));
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/structure/util/reference/ReferenceVertexTest.java