Add _metadata.get_project_id.
diff --git a/tests/test__default.py b/tests/test__default.py
index 747bfa4..e244b3d 100644
--- a/tests/test__default.py
+++ b/tests/test__default.py
@@ -214,7 +214,8 @@
 @mock.patch(
     'google.auth.compute_engine._metadata.ping', return_value=True)
 @mock.patch(
-    'google.auth.compute_engine._metadata.get', return_value='example-project')
+    'google.auth.compute_engine._metadata.get_project_id',
+    return_value='example-project')
 def test__get_gce_credentials(get_mock, ping_mock):
     credentials, project_id = _default._get_gce_credentials()
 
@@ -233,7 +234,7 @@
 @mock.patch(
     'google.auth.compute_engine._metadata.ping', return_value=True)
 @mock.patch(
-    'google.auth.compute_engine._metadata.get',
+    'google.auth.compute_engine._metadata.get_project_id',
     side_effect=exceptions.TransportError())
 def test__get_gce_credentials_no_project_id(get_mock, ping_mock):
     credentials, project_id = _default._get_gce_credentials()