@Test(expected = IllegalStateException.class)
        public void shouldNotConstructWithoutPartitionKey() {
            PartitionStrategy.build().create();
        }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/traversal/strategy/decoration/PartitionStrategyTest.java