Calling org.apache.tomcat.util.modeler.Registry.disableRegistry() assigns an instance of NoDescriptorRegistry to the static registry field. Subsequent invocations then log a warning that states that the registry cannot be disabled as it has already been initialised. These feels like a false-positive to me when registry is an instance of NoDescriptorRegistry. To avoid the unwanted warning, could the check be changed to something like the following:

if (registry == null) {
    registry = new NoDescriptorRegistry();
} else if (!registry instanceof NoDescriptorRegistry) {
    log.warn(sm.getString("registry.noDisable"));
}

This would improve log output in integration tests using embedded Tomcat where Tomcat may be initialised multiple times.