@Test(expected = IllegalStateException.class)
    public void shouldRequireGraphFormatIfLocationIsSet() {
        final Configuration conf = new BaseConfiguration();
        conf.setProperty(TinkerGraph.GREMLIN_TINKERGRAPH_GRAPH_LOCATION, TestHelper.makeTestDataDirectory(TinkerGraphTest.class));
        TinkerGraph.open(conf);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
@author Stephen Mallette (http://stephen.genoprime.com)
tinkergraph-gremlin/src/test/java/org/apache/tinkerpop/gremlin/tinkergraph/structure/TinkerGraphTest.java