@Before
    public void setup()  {
        g = traversal().withEmbedded(EmptyGraph.instance());
        antlrToLanguage = new GremlinAntlrToJava(g);
    }
Can only test against {@link EmptyGraph} which won't support transactions so all it can verify is that {@code tx()}
is called to fail.
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/language/grammar/TraversalSourceTxVisitorTest.java