Loading of client_secrets JSON file backed by a cache.

Contributed by crhyme.

Reviwed in http://codereview.appspot.com/6349087/.
diff --git a/tests/test_oauth2client_clientsecrets.py b/tests/test_oauth2client_clientsecrets.py
index 20cdf14..f69fb36 100644
--- a/tests/test_oauth2client_clientsecrets.py
+++ b/tests/test_oauth2client_clientsecrets.py
@@ -26,6 +26,11 @@
 from oauth2client import clientsecrets
 
 
+DATA_DIR = os.path.join(os.path.dirname(__file__), 'data')
+VALID_FILE = os.path.join(DATA_DIR, 'client_secrets.json')
+INVALID_FILE = os.path.join(DATA_DIR, 'unfilled_client_secrets.json')
+NONEXISTENT_FILE = os.path.join(__file__, '..', 'afilethatisntthere.json')
+
 class OAuth2CredentialsTests(unittest.TestCase):
 
   def setUp(self):
@@ -69,12 +74,72 @@
 
   def test_load_by_filename(self):
     try:
-      clientsecrets.loadfile(os.path.join(__file__, '..',
-                             'afilethatisntthere.json'))
+      clientsecrets._loadfile(NONEXISTENT_FILE)
       self.fail('should fail to load a missing client_secrets file.')
     except clientsecrets.InvalidClientSecretsError, e:
       self.assertTrue(str(e).startswith('File'))
 
 
+class CachedClientsecretsTests(unittest.TestCase):
+
+  class CacheMock(object):
+    def __init__(self):
+      self.cache = {}
+      self.last_get_ns = None
+      self.last_set_ns = None
+
+    def get(self, key, namespace=''):
+      # ignoring namespace for easier testing
+      self.last_get_ns = namespace
+      return self.cache.get(key, None)
+
+    def set(self, key, value, namespace=''):
+      # ignoring namespace for easier testing
+      self.last_set_ns = namespace
+      self.cache[key] = value
+
+  def setUp(self):
+    self.cache_mock = self.CacheMock()
+
+  def test_cache_miss(self):
+    client_type, client_info = clientsecrets.loadfile(
+      VALID_FILE, cache=self.cache_mock)
+    self.assertEquals('web', client_type)
+    self.assertEquals('foo_client_secret', client_info['client_secret'])
+
+    cached = self.cache_mock.cache[VALID_FILE]
+    self.assertEquals({client_type: client_info}, cached)
+
+    # make sure we're using non-empty namespace
+    ns = self.cache_mock.last_set_ns
+    self.assertTrue(bool(ns))
+    # make sure they're equal
+    self.assertEquals(ns, self.cache_mock.last_get_ns)
+
+  def test_cache_hit(self):
+    self.cache_mock.cache[NONEXISTENT_FILE] = { 'web': 'secret info' }
+
+    client_type, client_info = clientsecrets.loadfile(
+      NONEXISTENT_FILE, cache=self.cache_mock)
+    self.assertEquals('web', client_type)
+    self.assertEquals('secret info', client_info)
+    # make sure we didn't do any set() RPCs
+    self.assertEqual(None, self.cache_mock.last_set_ns)
+
+  def test_validation(self):
+    try:
+      clientsecrets.loadfile(INVALID_FILE, cache=self.cache_mock)
+      self.fail('Expected InvalidClientSecretsError to be raised '
+                'while loading %s' % INVALID_FILE)
+    except clientsecrets.InvalidClientSecretsError:
+      pass
+
+  def test_without_cache(self):
+    # this also ensures loadfile() is backward compatible
+    client_type, client_info = clientsecrets.loadfile(VALID_FILE)
+    self.assertEquals('web', client_type)
+    self.assertEquals('foo_client_secret', client_info['client_secret'])
+
+
 if __name__ == '__main__':
   unittest.main()