Starting with Jenkins core 2.85, testInProgress does not show anything when clicking on the "Test progress report" action. The Log file says:
Dez 08, 2017 7:47:40 AM org.jenkinsci.testinprogress.server.messages.AllVersionsTestMessagesParser processTestMessages
WARNUNG: Could not read message
java.io.IOException: Unknown message format :
at org.jenkinsci.testinprogress.server.messages.AllVersionsTestMessagesParser.processTestMessages(AllVersionsTestMessagesParser.java:45)
at org.jenkinsci.testinprogress.server.events.TestEventsReceiver.run(TestEventsReceiver.java:41)
at java.lang.Thread.run(Thread.java:748)
Also, there are no longer .events files under unitevents/. As far as I can tell, it seems like it has to do with changes on the remoting version, introduced with the Jenkins core 2.85.