update test for fake reader decorator

python/paddle/reader/tests/decorator_test.py

@@ -211,6 +211,7 @@ class TestFakeReader(unittest.TestCase):
 
         data_num = 100
         fake_reader = paddle.reader.fake(reader, data_num)
+        for _ in range(10):
             i = 0
             for data in fake_reader():
                 self.assertEqual(data, 0)