ModelNode addOp = new ModelNode();
addOp.get(OP).set(WRITE_ATTRIBUTE_OPERATION);
addOp.get(OP_ADDR).set(agentSubsystemPath.toModelNode());
addOp.get(NAME).set(AgentSubsystemExtension.PLUGINS_ELEMENT);
addOp.get(VALUE).set(pluginsNode);
ModelNode result = services.executeOperation(addOp);
Assert.assertEquals(result.get(OUTCOME).asString(), SUCCESS);
// now test that things are as they should be
model = services.readWholeModel();
Assert.assertTrue(model.get(SUBSYSTEM).hasDefined(AgentSubsystemExtension.SUBSYSTEM_NAME));