[Predator] Add local cache for get command output.

appengine/findit/common/test/cache_decorator_test.py

Index: appengine/findit/common/test/cache_decorator_test.py
diff --git a/appengine/findit/common/test/cache_decorator_test.py b/appengine/findit/common/test/cache_decorator_test.py
index a3a2fd467c7e0b29790a484bd2e45b31d958614c..2be1439799f2c522ace750facf404cef44a7b1ba 100644
--- a/appengine/findit/common/test/cache_decorator_test.py
+++ b/appengine/findit/common/test/cache_decorator_test.py
@@ -2,6 +2,9 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import __builtin__
+import mock
+import os
 import pickle
 import zlib
 
@@ -162,3 +165,19 @@ class CacheDecoratorTest(testing.AppengineTestCase):
     a2 = A('http://test', 5)
     self.assertEqual('http://test/p1', a2.Func('p1'))
     self.assertEqual(0, a2.runs)
+
+  def testLocalCacher(self):
+    fake_dir = 'fake_dir'
+    cacher = cache_decorator.LocalCacher(cache_dir=fake_dir)
+    def _MockPathExists(path, *_):
+      return False if path == os.path.join(
+          fake_dir, 'uncached_key') else True
+    self.mock(os.path, 'exists', _MockPathExists)
+
+    value = 'value'
+    with mock.patch('__builtin__.open', mock.mock_open(
+        read_data=zlib.compress(pickle.dumps('value')))) as m:
+      cacher.Set('a', 'b')
+      m.assert_called_once_with(os.path.join(fake_dir, 'a'), 'wb')
+      self.assertEqual(value, cacher.Get('key'))
+      self.assertIsNone(cacher.Get('uncached_key'))