diff --git a/tests/oauth2/test_credentials.py b/tests/oauth2/test_credentials.py
new file mode 100644
index 0000000..173bb00
--- /dev/null
+++ b/tests/oauth2/test_credentials.py
@@ -0,0 +1,79 @@
+# Copyright 2016 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import datetime
+
+import mock
+import pytest
+
+from google.auth import _helpers
+from google.oauth2 import credentials
+
+
+class TestCredentials(object):
+    TOKEN_URI = 'https://example.com/oauth2/token'
+    REFRESH_TOKEN = 'refresh_token'
+    CLIENT_ID = 'client_id'
+    CLIENT_SECRET = 'client_secret'
+
+    @pytest.fixture(autouse=True)
+    def credentials(self):
+        self.credentials = credentials.Credentials(
+            token=None, refresh_token=self.REFRESH_TOKEN,
+            token_uri=self.TOKEN_URI, client_id=self.CLIENT_ID,
+            client_secret=self.CLIENT_SECRET)
+
+    def test_default_state(self):
+        assert not self.credentials.valid
+        # Expiration hasn't been set yet
+        assert not self.credentials.expired
+        # Scopes aren't required for these credentials
+        assert not self.credentials.requires_scopes
+
+    def test_create_scoped(self):
+        with pytest.raises(NotImplementedError):
+            self.credentials.with_scopes(['email'])
+
+    @mock.patch('google.oauth2._client.refresh_grant')
+    @mock.patch(
+        'google.auth._helpers.utcnow', return_value=datetime.datetime.min)
+    def test_refresh_success(self, now_mock, refresh_grant_mock):
+        token = 'token'
+        expiry = _helpers.utcnow() + datetime.timedelta(seconds=500)
+        refresh_grant_mock.return_value = (
+            # Access token
+            token,
+            # New refresh token
+            None,
+            # Expiry,
+            expiry,
+            # Extra data
+            {})
+        request_mock = mock.Mock()
+
+        # Refresh credentials
+        self.credentials.refresh(request_mock)
+
+        # Check jwt grant call.
+        refresh_grant_mock.assert_called_with(
+            request_mock, self.TOKEN_URI, self.REFRESH_TOKEN, self.CLIENT_ID,
+            self.CLIENT_SECRET)
+
+        # Check that the credentials have the token and expiry
+        assert self.credentials.token == token
+        assert self.credentials.expiry == expiry
+
+        # Check that the credentials are valid (have a token and are not
+        # expired)
+        assert self.credentials.valid