@Override
        public Integer generateFinalResult(final Iterator<KeyValue<NullObject, Integer>> keyValues) {
            int counter = keyValues.next().getValue();
            assertFalse(keyValues.hasNext());

            switch (this.state) {
                case VertexProgramM.SOFTWARE_ONLY: {
                    assertEquals(2, counter);
                    break;
                }
                case VertexProgramM.PEOPLE_ONLY: {
                    assertEquals(4, counter);
                    break;
                }
                case VertexProgramM.KNOWS_ONLY: {
                    assertEquals(6, counter);
                    break;
                }
                case VertexProgramM.PEOPLE_KNOWS_ONLY: {
                    assertEquals(4, counter);
                    break;
                }
                case VertexProgramM.PEOPLE_KNOWS_WELL_ONLY: {
                    assertEquals(4, counter);
                    break;
                }
                case VertexProgramM.VERTICES_ONLY: {
                    assertEquals(6, counter);
                    break;
                }
                case VertexProgramM.ONE_OUT_EDGE_ONLY: {
                    assertEquals(6, counter);
                    break;
                }
                case VertexProgramM.OUT_EDGES_ONLY: {
                    assertEquals(6, counter);
                    break;
                }
                default:
                    throw new IllegalStateException("This is an illegal state for this test case: " + this.state);
            }
            return counter;
        }
Javadoc for {@code ConcurrentSkipListSet} includes this little note: "Beware that, unlike in most
collections, the size method is not a constant-time operation." Doing a traversal of elements will yield
the correct count. Java 11 upgrade seemed to force this failure consistently.
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/computer/GraphComputerTest.java