add ability to pickle tftest instance objects (#56)

* add test_pickle.py

* add skip duner method cond and __*state__ methods

* add linting changes

* linting changes attempt 2

* lint changes tftest.py

test/test_pickle.py

@@ -0,0 +1,59 @@
+# Copyright 2019 Google LLC
+#
+# 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
+#
+#     https://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.
+
+"Test serialization of tftest instances"
+
+import pytest
+import tftest
+import pickle
+
+
+def assert_pickle_flow(obj):
+  """Ensures instance is the same after being pickled"""
+  pickled_obj = pickle.dumps(obj)
+  pickled_obj = pickle.loads(pickled_obj)
+  assert isinstance(pickled_obj, type(obj))
+
+
+@pytest.fixture(scope="module")
+def tf(fixtures_dir):
+  tf = tftest.TerraformTest("plan_no_resource_changes", fixtures_dir)
+  tf.setup()
+  return tf
+
+
+def test_setup(fixtures_dir):
+  tf = tftest.TerraformTest("plan_no_resource_changes", fixtures_dir)
+  expected = tf.setup()
+  assert_pickle_flow(expected)
+
+
+def test_plan(tf):
+  expected = tf.plan(output=True)
+  assert_pickle_flow(expected)
+
+
+def test_apply(tf):
+  expected = tf.apply()
+  assert_pickle_flow(expected)
+
+
+def test_output(tf):
+  expected = tf.output()
+  assert_pickle_flow(expected)
+
+
+def test_state_pull(tf):
+  expected = tf.state_pull()
+  assert_pickle_flow(expected)

tftest.py

@@ -174,6 +174,9 @@ def __init__(self, raw):
     self.sensitive = tuple(k for k, v in raw.items() if v.get('sensitive'))
 
   def __getattr__(self, name):
+    if isinstance(name, str) and name[:2] == name[-2:] == '__':
+      # skip non-existing dunder method lookups
+      raise AttributeError(name)
     return getattr(self._raw, name)
 
   def __getitem__(self, name):
@@ -241,6 +244,12 @@ def modules(self):
   def __getattr__(self, name):
     return self._raw[name]
 
+  def __getstate__(self):
+    return self.__dict__
+
+  def __setstate__(self, d):
+    self.__dict__.update(d)
+
 
 class TerraformState(TerraformJSONBase):
   "Minimal wrapper for Terraform state JSON format."
@@ -264,6 +273,12 @@ def resources(self):
   def __getattr__(self, name):
     return self._raw[name]
 
+  def __getstate__(self):
+    return self.__dict__
+
+  def __setstate__(self, d):
+    self.__dict__.update(d)
+
 
 class TerraformTest(object):
   """Helper class for use in testing Terraform modules.