first add files

lib/greenlet/tests/test_stack_saved.py

@@ -0,0 +1,19 @@
+import greenlet
+import unittest
+
+
+class Test(unittest.TestCase):
+
+    def test_stack_saved(self):
+        main = greenlet.getcurrent()
+        self.assertEqual(main._stack_saved, 0)
+
+        def func():
+            main.switch(main._stack_saved)
+
+        g = greenlet.greenlet(func)
+        x = g.switch()
+        assert x > 0, x
+        assert g._stack_saved > 0, g._stack_saved
+        g.switch()
+        assert g._stack_saved == 0, g._stack_saved