@Test(expected = IllegalArgumentException.class)
    public void shouldFailPropertyWithCardinalityNullVertexId() {
        g.addV().property(VertexProperty.Cardinality.single, T.id, null);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/traversal/dsl/graph/GraphTraversalTest.java