@Test
    public void shouldBeSameInstance() {
        final Set<GremlinScriptEngine> scriptEngines = new HashSet<>();
        IntStream.range(0,100).forEach(i -> scriptEngines.add(manager.getEngineByName(ENGINE_TO_TEST)));
        assertEquals(1, scriptEngines.size());
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/jsr223/CachedGremlinScriptEngineManagerTest.java