@Test
    public void shouldGenerateNiceErrorOnConversionOfEmptyStringToString() {
        exceptionRule.expect(IllegalArgumentException.class);
        exceptionRule.expectMessage("Expected a non-empty string but received an empty string.");
        final TinkerGraph.IdManager manager = TinkerGraph.DefaultIdManager.STRING;
        manager.convert("");
    }
@author Stephen Mallette (http://stephen.genoprime.com)
tinkergraph-gremlin/src/test/java/org/apache/tinkerpop/gremlin/tinkergraph/structure/IdManagerTest.java