If we have opened JDTS in tester mode with wd, based on all.jtm template, and try to create new wd, based on readiness.jtm template, we may see:

Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 2 >= 1
            at java.util.Vector.elementAt(Vector.java:427)
            at javax.swing.tree.DefaultMutableTreeNode.getChildAt(DefaultMutableTreeNode.java:230)
            at javax.swing.tree.VariableHeightLayoutCache.treeNodesRemoved(VariableHeightLayoutCache.java:543)
            at javax.swing.plaf.basic.BasicTreeUI$Handler.treeNodesRemoved(BasicTreeUI.java:3810)
            at com.sun.javatest.exec.TestTreeModel$Notifier.run(TestTreeModel.java:1507)
            at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
            at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
            at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
            at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
            at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
            at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
            at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
            at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

it doesn't breaks tree functionality, but visible inside jdts console.

The root cause is removing tree nodes from JTree, from ContextManager.refreshIfNeeded().
Stack trace:

        at java.lang.Thread.dumpStack(Thread.java:1206)
        at com.sun.javatest.TestResultTable.notifyRemoveLeaf(TestResultTable.java:1856)
        at com.sun.javatest.TRT_TreeNode.rmChild(TRT_TreeNode.java:1564)
        at com.sun.javatest.TRT_TreeNode.refreshIfNeeded(TRT_TreeNode.java:791)
        at com.sun.javatest.TestResultTable.recursiveRefresh(TestResultTable.java:1801)
        at com.sun.javatest.TestResultTable.refreshIfNeeded(TestResultTable.java:1377)
        at com.sun.javatest.exec.ContextManager.refreshTestsImpl(ContextManager.java:308)
        at com.sun.javatest.exec.ContextManager.access$000(ContextManager.java:75)
        at com.sun.javatest.exec.ContextManager$1.run(ContextManager.java:242)
        at java.lang.Thread.run(Thread.java:619)