add comment for test case

Author: jschneider

src/test/java/io/reactivex/schedulers/NewThreadSchedulerTest.java

@@ -116,12 +116,16 @@ public void run() {
         assertEquals(0, calls[0]);
     }
 
+    /**
+     * Regression test to ensure there is no NPE when the worker has been disposed
+     */
     @Test
     public void npe() throws Exception {
         Scheduler s = getScheduler();
         NewThreadWorker w = (NewThreadWorker) s.createWorker();
         w.dispose();
 
+        //This method used to throw a NPE when the worker has been disposed and the parent is null
         w.scheduleActual(new Runnable() {
             @Override
             public void run() {