@Override
        public void map(final Vertex vertex, final MapEmitter<NullObject, Integer> emitter) {
            emitter.emit(1);
            switch (this.state) {
                case VertexProgramM.SOFTWARE_ONLY: {
                    assertEquals("software", vertex.label());
                    break;
                }
                case VertexProgramM.PEOPLE_ONLY: {
                    assertEquals("person", vertex.label());
                    break;
                }
                case VertexProgramM.KNOWS_ONLY: {
                    assertTrue(vertex.label().equals("person") || vertex.label().equals("software"));
                    break;
                }
                case VertexProgramM.PEOPLE_KNOWS_ONLY: {
                    assertEquals("person", vertex.label());
                    break;
                }
                case VertexProgramM.PEOPLE_KNOWS_WELL_ONLY: {
                    assertEquals("person", vertex.label());
                    break;
                }
                case VertexProgramM.VERTICES_ONLY: {
                    assertTrue(vertex.label().equals("person") || vertex.label().equals("software"));
                    break;
                }
                case VertexProgramM.ONE_OUT_EDGE_ONLY: {
                    assertTrue(vertex.label().equals("person") || vertex.label().equals("software"));
                    break;
                }
                case VertexProgramM.OUT_EDGES_ONLY: {
                    assertTrue(vertex.label().equals("person") || vertex.label().equals("software"));
                    break;
                }
                default:
                    throw new IllegalStateException("This is an illegal state for this test case: " + this.state);
            }
        }
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