https://github.com/wildfly/wildfly-core/blob/master/testsuite/domain/src/test/java/org/jboss/as/test/integration/domain/events/ProcessStateListenerTestCase.java
https://github.com/wildfly/wildfly-core/blob/master/testsuite/manualmode/src/test/java/org/wildfly/core/test/standalone/mgmt/events/ProcessStateListenerTestCase.java

• test more possible transitions, e.g. reload-required
• test listener that raises exception in stateChanged* methods
• test execution timeout
• ....