Adding tox env for datastore sys tests w / emulator.

CONTRIBUTING.rst

@@ -212,8 +212,14 @@ Running System Tests
    $ python system_tests/clear_datastore.py
 
 - System tests can also be run against local `emulators`_ that mock
-  the production services. For example, to run the system tests
-  with the ``datastore`` emulator, first start the emulator and
+  the production services. To run the system tests with the
+  ``datastore`` emulator::
+
+   $ tox -e datastore-emulator
+
+  This also requires that the ``gcloud`` command line tool is
+  installed. If you'd like to run them directly (outside of a
+  ``tox`` environment), first start the emulator and
   take note of the process ID::
 
    $ gcloud beta emulators datastore start &

scripts/datastore_emulator.py

@@ -0,0 +1,65 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# 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.
+
+"""Run datastore system tests locally with the datastore emulator.
+
+First makes system calls to spawn the datastore emulator and get
+the local environment variables needed for it. Then calls the
+datastore system tests.
+"""
+
+
+import os
+import subprocess
+
+from gcloud.environment_vars import GCD_DATASET
+from gcloud.environment_vars import GCD_HOST
+
+
+_START_CMD = ('gcloud', 'beta', 'emulators', 'datastore', 'start')
+_ENV_INIT_CMD = ('gcloud', 'beta', 'emulators', 'datastore', 'env-init')
+_HOST_VAR_NAME = 'DATASTORE_HOST'
+_DATASET_PREFIX = 'export ' + GCD_DATASET + '='
+_HOST_LINE_PREFIX = 'export ' + GCD_HOST + '='
+
+
+def main():
+    """Spawn an emulator instance and run the datastore system tests."""
+    # Ignore stdin and stdout, don't pollute the user's output with them.
+    proc_start = subprocess.Popen(_START_CMD, stdout=subprocess.PIPE,
+                                  stderr=subprocess.PIPE)
+    try:
+        env_lines = subprocess.check_output(
+            _ENV_INIT_CMD).strip().split('\n')
+        dataset, = [line.split(_DATASET_PREFIX, 1)[1] for line in env_lines
+                    if line.startswith(_DATASET_PREFIX)]
+        host, = [line.split(_HOST_LINE_PREFIX, 1)[1] for line in env_lines
+                 if line.startswith(_HOST_LINE_PREFIX)]
+        # Set environment variables before running the system tests.
+        os.environ[GCD_DATASET] = dataset
+        os.environ[GCD_HOST] = host
+        os.environ['GCLOUD_NO_PRINT'] = 'true'
+        # Delay import until after environment variables are set.
+        from system_tests.run_system_test import run_module_tests
+        run_module_tests('datastore',
+                         ignore_requirements=True)
+    finally:
+        # NOTE: This is mostly defensive. Since ``proc_start`` will be spawned
+        #       by this current process, it should be killed when this process
+        #       exits whether or not we kill it.
+        proc_start.kill()
+
+
+if __name__ == '__main__':
+    main()

tox.ini

@@ -89,3 +89,9 @@ basepython =
 commands =
     python {toxinidir}/scripts/attempt_system_tests.py
 passenv = {[testenv:system-tests]passenv}
+
+[testenv:datastore-emulator]
+basepython =
+    python2.7
+commands =
+    python {toxinidir}/scripts/datastore_emulator.py