@Test(expected = FastNoSuchElementException.class)
    public void shouldThrowFastNoSuchElementExceptionIfEmptyIteratorIsAdded() {
        final MultiIterator<String> itty = new MultiIterator<>();
        itty.addIterator(EmptyIterator.instance());
        itty.next();
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/util/iterator/MultiIteratorTest.java