int oldRule = changeDeleteRule(DeleteRule.DENY);
try {
DeleteRuleFlatA a = context.newObject(DeleteRuleFlatA.class);
DeleteRuleFlatB b = context.newObject(DeleteRuleFlatB.class);
a.addToFlatB(b);
context.commitChanges();
try {
context.deleteObject(a);
fail("Must have thrown a deny exception..");