private Object eval(final String query) {
        final GremlinLexer lexer = new GremlinLexer(CharStreams.fromString(query));
        final GremlinParser parser = new GremlinParser(new CommonTokenStream(lexer));
        return antlrToLanguage.visit(parser.queryList());
    }
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