below snippet hangs(or just timeout) when tests
        List<Integer> empty = new ArrayList<>();
        int selected = 3;
        Stream<Integer> sToBeConcated = empty.stream();
        for(int i = 0; i < 32; i++){
            final int i1 = i;
            sToBeConcated = Streams.concat(sToBeConcated, Streams.generateInt(() -> i1 + 1).limit(selected == 3 ? i + 1 : 1 << 6).boxed());
        }
        System.out.println(sToBeConcated.toArray().length);

This caused below lambda tests failed
java/util/stream/Stream/IntStreamTest.java

Test log shows
java.lang.NullPointerException
at com.sun.javatest.regtest.TestNGReporter.getMatcher(TestNGReporter.java:97)
at com.sun.javatest.regtest.TestNGReporter.add(TestNGReporter.java:80)
at com.sun.javatest.regtest.TestNGAction.endAction(TestNGAction.java:127)
at com.sun.javatest.regtest.MainAction.run(MainAction.java:252)
at com.sun.javatest.regtest.RegressionScript.run(RegressionScript.java:146)
at com.sun.javatest.Script.run(Script.java:228)
at com.sun.javatest.DefaultTestRunner.runTest(DefaultTestRunner.java:174)
at com.sun.javatest.DefaultTestRunner.access$100(DefaultTestRunner.java:43)
at com.sun.javatest.DefaultTestRunner$1.run(DefaultTestRunner.java:66)
Which is because hanging cause timeout, and no testng report is available