@Test
    @FeatureRequirement(featureClass = Graph.Features.GraphFeatures.class, feature = Graph.Features.GraphFeatures.FEATURE_TRANSACTIONS)
    public void shouldAllowAutoTransactionToWorkWithoutMutationByDefault() {
        // expecting no exceptions to be thrown here
        g.tx().commit();
        assertThat(g.tx().isOpen(), is(false));
        g.tx().rollback();
        assertThat(g.tx().isOpen(), is(false));
        g.tx().commit();
        assertThat(g.tx().isOpen(), is(false));
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/structure/TransactionTest.java