@Test
    public void shouldWriteModernGraphAsGraphML() throws IOException {
        try (final OutputStream os = new FileOutputStream(new File(tempPath, "tinkerpop-modern.xml"))) {
            GraphMLWriter.build().create().writeGraph(os, TinkerFactory.createModern());
        }
    }
No assertions.  Just write out the graph for convenience.
tinkergraph-gremlin/src/test/java/org/apache/tinkerpop/gremlin/tinkergraph/structure/IoDataGenerationTest.java