Check if processes are alive in test. (#261)

test/stress_tests.py

@@ -93,6 +93,8 @@ class TaskTests(unittest.TestCase):
     n = 10 ** 4 # TODO(pcm): replace by 10 ** 5 once this is faster
     l = ray.get([f.remote() for _ in range(n)])
     self.assertEqual(l, n * [1])
+
+    self.assertTrue(ray.services.all_processes_alive())
     ray.worker.cleanup()
 
   def testWait(self):