[rllib] Fix testGetFilters in A3C (#1557)

python/ray/rllib/test/test_evaluators.py

@@ -6,6 +6,7 @@ import unittest
 import gym
 import shutil
 import tempfile
+import time
 
 import ray
 from ray.rllib.a3c import DEFAULT_CONFIG
@@ -51,6 +52,7 @@ class A3CEvaluatorTest(unittest.TestCase):
 
     def sample_and_flush(self):
         e = self.e
+        time.sleep(2)
         self.e.sample()
         filters = e.get_filters(flush_after=True)
         obs_f = filters["obs_filter"]
@@ -62,14 +64,15 @@ class A3CEvaluatorTest(unittest.TestCase):
         return obs_f, rew_f
 
     def testGetFilters(self):
+        """Show `flush_after=False` provides does not affect the buffer."""
         e = self.e
-        obs_f, rew_f = self.sample_and_flush()
-        COUNT = obs_f.rs.n
+        self.sample_and_flush()
         filters = e.get_filters(flush_after=False)
         obs_f = filters["obs_filter"]
-        NEW_COUNT = obs_f.rs.n
-        self.assertGreaterEqual(NEW_COUNT, COUNT)
-        self.assertLessEqual(obs_f.buffer.n, NEW_COUNT - COUNT)
+        filters2 = e.get_filters(flush_after=False)
+        obs_f2 = filters2["obs_filter"]
+        self.assertGreaterEqual(obs_f2.rs.n, obs_f.rs.n)
+        self.assertGreaterEqual(obs_f2.buffer.n, obs_f.buffer.n)
 
     def testSyncFilter(self):
         """Show that sync_filters rebases own buffer over input"""