public Handler getHandler(String clusterId, String componentId) {
        Component<?,?> component = getComponent(clusterId, componentId);
        if (! (component instanceof Handler))
            throw new RuntimeException("Component is not a handler: " + componentId);
        return (Handler) component;
    }
Utility functions for testing the ContainerModelBuilder. Note that XML validation will
not be done when using this class

@author gjoranv
config-model/src/test/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilderTestBase.java