Add api_core package (#4210)

* Add api_core package

* Address review comments
diff --git a/tests/unit/operations_v1/test_operations_client.py b/tests/unit/operations_v1/test_operations_client.py
new file mode 100644
index 0000000..60b11b7
--- /dev/null
+++ b/tests/unit/operations_v1/test_operations_client.py
@@ -0,0 +1,101 @@
+# Copyright 2017 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 mock
+
+from google.api_core import operations_v1
+from google.api_core import page_iterator
+from google.longrunning import operations_pb2
+
+
+def make_operations_stub(channel):
+    return mock.Mock(
+        spec=[
+            'GetOperation', 'DeleteOperation', 'ListOperations',
+            'CancelOperation'])
+
+
+operations_stub_patch = mock.patch(
+    'google.longrunning.operations_pb2.OperationsStub',
+    autospec=True,
+    side_effect=make_operations_stub)
+
+
+@operations_stub_patch
+def test_constructor(operations_stub):
+    stub = make_operations_stub(None)
+    operations_stub.side_effect = None
+    operations_stub.return_value = stub
+
+    client = operations_v1.OperationsClient(mock.sentinel.channel)
+
+    assert client.operations_stub == stub
+    operations_stub.assert_called_once_with(mock.sentinel.channel)
+
+
+@operations_stub_patch
+def test_get_operation(operations_stub):
+    client = operations_v1.OperationsClient(mock.sentinel.channel)
+    client.operations_stub.GetOperation.return_value = mock.sentinel.operation
+
+    response = client.get_operation('name')
+
+    request = client.operations_stub.GetOperation.call_args[0][0]
+    assert isinstance(request, operations_pb2.GetOperationRequest)
+    assert request.name == 'name'
+
+    assert response == mock.sentinel.operation
+
+
+@operations_stub_patch
+def test_list_operations(operations_stub):
+    client = operations_v1.OperationsClient(mock.sentinel.channel)
+    operations = [
+        operations_pb2.Operation(name='1'),
+        operations_pb2.Operation(name='2')]
+    list_response = operations_pb2.ListOperationsResponse(
+        operations=operations)
+    client.operations_stub.ListOperations.return_value = list_response
+
+    response = client.list_operations('name', 'filter')
+
+    assert isinstance(response, page_iterator.Iterator)
+    assert list(response) == operations
+
+    request = client.operations_stub.ListOperations.call_args[0][0]
+    assert isinstance(request, operations_pb2.ListOperationsRequest)
+    assert request.name == 'name'
+    assert request.filter == 'filter'
+
+
+@operations_stub_patch
+def test_delete_operation(operations_stub):
+    client = operations_v1.OperationsClient(mock.sentinel.channel)
+
+    client.delete_operation('name')
+
+    request = client.operations_stub.DeleteOperation.call_args[0][0]
+    assert isinstance(request, operations_pb2.DeleteOperationRequest)
+    assert request.name == 'name'
+
+
+@operations_stub_patch
+def test_cancel_operation(operations_stub):
+    client = operations_v1.OperationsClient(mock.sentinel.channel)
+
+    client.cancel_operation('name')
+
+    request = client.operations_stub.CancelOperation.call_args[0][0]
+    assert isinstance(request, operations_pb2.CancelOperationRequest)
+    assert request.name == 'name'