JDK-8347491 introduced

 Objects.requireNonNull(unit, "unit");

but the sub-test in

java/util/concurrent/tck/JSR166TestCase.java

expects to get a "real" NPE:

STARTED ThreadPoolExecutorTest::testTimedInvokeAnyNullTimeUnit 'testTimedInvokeAnyNullTimeUnit'
junit.framework.ComparisonFailure: expected:<Cannot invoke "java.util.concurrent.TimeUnit.toNanos(long)" because "unit" is null> but was:<null>
at junit.framework.Assert.assertEquals(Assert.java:100)
at junit.framework.Assert.assertEquals(Assert.java:107)
at junit.framework.TestCase.assertEquals(TestCase.java:260)
at ThreadPoolExecutorTest.testTimedInvokeAnyNullTimeUnit(ThreadPoolExecutorTest.java:1730)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:565)
at junit.framework.TestCase.runTest(TestCase.java:177)
at JSR166TestCase.runTest(JSR166TestCase.java:382)
at junit.framework.TestCase.runBare(TestCase.java:142)
at JSR166TestCase.runBare(JSR166TestCase.java:373)
at junit.framework.TestResult$1.protect(TestResult.java:122)
at junit.framework.TestResult.runProtected(TestResult.java:142)
at junit.framework.TestResult.run(TestResult.java:125)
at junit.framework.TestCase.run(TestCase.java:130)
at junit.framework.TestSuite.runTest(TestSuite.java:241)
at junit.framework.TestSuite.run(TestSuite.java:236)
at junit.framework.TestSuite.runTest(TestSuite.java:241)
at junit.framework.TestSuite.run(TestSuite.java:236)

Not clear why the msg is actually null though.