We had the following test failure on our nightly test run last night:

javafx.concurrent.TaskSwampEventQueueTest > numberOfEventsOnTheEventQueueShouldNeverBeLarge FAILED
    java.lang.AssertionError:
        at org.junit.Assert.fail(Assert.java:91)
        at org.junit.Assert.assertTrue(Assert.java:43)
        at org.junit.Assert.assertTrue(Assert.java:54)
        at javafx.concurrent.TaskSwampEventQueueTest.numberOfEventsOnTheEventQueueShouldNeverBeLarge(TaskSwampEventQueueTest.java:95)

I've seen this fail very rarely on my personal machine (usually when the system was busy running something else at the same time).