@Test
    @FeatureRequirement(featureClass = Graph.Features.VertexFeatures.class, feature = Graph.Features.VertexFeatures.FEATURE_ADD_VERTICES)
    @FeatureRequirement(featureClass = Graph.Features.GraphFeatures.class, feature = FEATURE_TRANSACTIONS)
    public void shouldHaveExceptionConsistencyWhenUsingManualTransactionOnRollback() {
        g.tx().onReadWrite(Transaction.READ_WRITE_BEHAVIOR.MANUAL);

        try {
            g.tx().rollback();
            fail("An exception should be thrown when read/write behavior is manual and no transaction is opened");
        } catch (Exception ex) {
            validateException(Transaction.Exceptions.transactionMustBeOpenToReadWrite(), ex);
        }
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/structure/TransactionTest.java