tests: Add a context manager function in test helpers.

This function can be used to ensure that mocker objects 
are restored and verified during usage if exceptions are 
thrown while the mock object is being used.

Ensure it is used in the config drive test when multiple
mock objects are being created and restored.

LP: #1098430

2 files changed, 53 insertions, 41 deletions

diff --git a/tests/unittests/helpers.py b/tests/unittests/helpers.py
index 92540b0c..4258a29d 100644
--- a/tests/unittests/helpers.py
+++ b/tests/unittests/helpers.py
@@ -2,6 +2,9 @@ import os
 import sys
 import unittest
 
+from contextlib import contextmanager
+
+from mocker import Mocker
 from mocker import MockerTestCase
 
 from cloudinit import helpers as ch
@@ -31,6 +34,17 @@ else:
         pass
 
 
+@contextmanager
+def mocker(verify_calls=True):
+    m = Mocker()
+    try:
+        yield m
+    finally:
+        m.restore()
+        if verify_calls:
+            m.verify()
+
+
 # Makes the old path start
 # with new base instead of whatever
 # it previously had
diff --git a/tests/unittests/test_datasource/test_configdrive.py b/tests/unittests/test_datasource/test_configdrive.py
index aa5b98ed..6751a679 100644
--- a/tests/unittests/test_datasource/test_configdrive.py
+++ b/tests/unittests/test_datasource/test_configdrive.py
@@ -11,6 +11,7 @@ from cloudinit import settings
 from cloudinit.sources import DataSourceConfigDrive as ds
 from cloudinit import util
 
+from tests.unittests import helpers as unit_helpers
 
 PUBKEY = u'ssh-rsa AAAAB3NzaC1....sIkJhq8wdX+4I3A4cYbYP ubuntu@server-460\n'
 EC2_META = {
@@ -89,23 +90,22 @@ class TestConfigDriveDataSource(MockerTestCase):
             'swap': '/dev/vda3',
         }
         for name, dev_name in name_tests.items():
-            my_mock = mocker.Mocker()
-            find_mock = my_mock.replace(util.find_devs_with,
-                                        spec=False, passthrough=False)
-            provided_name = dev_name[len('/dev/'):]
-            provided_name = "s" + provided_name[1:]
-            find_mock(mocker.ARGS)
-            my_mock.result([provided_name])
-            exists_mock = my_mock.replace(os.path.exists,
-                                          spec=False, passthrough=False)
-            exists_mock(mocker.ARGS)
-            my_mock.result(False)
-            exists_mock(mocker.ARGS)
-            my_mock.result(True)
-            my_mock.replay()
-            device = cfg_ds.device_name_to_device(name)
-            my_mock.restore()
-            self.assertEquals(dev_name, device)
+            with unit_helpers.mocker() as my_mock:
+                find_mock = my_mock.replace(util.find_devs_with,
+                                            spec=False, passthrough=False)
+                provided_name = dev_name[len('/dev/'):]
+                provided_name = "s" + provided_name[1:]
+                find_mock(mocker.ARGS)
+                my_mock.result([provided_name])
+                exists_mock = my_mock.replace(os.path.exists,
+                                              spec=False, passthrough=False)
+                exists_mock(mocker.ARGS)
+                my_mock.result(False)
+                exists_mock(mocker.ARGS)
+                my_mock.result(True)
+                my_mock.replay()
+                device = cfg_ds.device_name_to_device(name)
+                self.assertEquals(dev_name, device)
 
     def test_dev_os_map(self):
         populate_dir(self.tmp, CFG_DRIVE_FILES_V2)
@@ -122,19 +122,18 @@ class TestConfigDriveDataSource(MockerTestCase):
             'swap': '/dev/vda3',
         }
         for name, dev_name in name_tests.items():
-            my_mock = mocker.Mocker()
-            find_mock = my_mock.replace(util.find_devs_with,
-                                        spec=False, passthrough=False)
-            find_mock(mocker.ARGS)
-            my_mock.result([dev_name])
-            exists_mock = my_mock.replace(os.path.exists,
-                                          spec=False, passthrough=False)
-            exists_mock(mocker.ARGS)
-            my_mock.result(True)
-            my_mock.replay()
-            device = cfg_ds.device_name_to_device(name)
-            my_mock.restore()
-            self.assertEquals(dev_name, device)
+            with unit_helpers.mocker() as my_mock:
+                find_mock = my_mock.replace(util.find_devs_with,
+                                            spec=False, passthrough=False)
+                find_mock(mocker.ARGS)
+                my_mock.result([dev_name])
+                exists_mock = my_mock.replace(os.path.exists,
+                                              spec=False, passthrough=False)
+                exists_mock(mocker.ARGS)
+                my_mock.result(True)
+                my_mock.replay()
+                device = cfg_ds.device_name_to_device(name)
+                self.assertEquals(dev_name, device)
 
     def test_dev_ec2_remap(self):
         populate_dir(self.tmp, CFG_DRIVE_FILES_V2)
@@ -156,17 +155,16 @@ class TestConfigDriveDataSource(MockerTestCase):
             'root2k': None,
         }
         for name, dev_name in name_tests.items():
-            my_mock = mocker.Mocker()
-            exists_mock = my_mock.replace(os.path.exists,
-                                          spec=False, passthrough=False)
-            exists_mock(mocker.ARGS)
-            my_mock.result(False)
-            exists_mock(mocker.ARGS)
-            my_mock.result(True)
-            my_mock.replay()
-            device = cfg_ds.device_name_to_device(name)
-            self.assertEquals(dev_name, device)
-            my_mock.restore()
+            with unit_helpers.mocker(verify_calls=False) as my_mock:
+                exists_mock = my_mock.replace(os.path.exists,
+                                              spec=False, passthrough=False)
+                exists_mock(mocker.ARGS)
+                my_mock.result(False)
+                exists_mock(mocker.ARGS)
+                my_mock.result(True)
+                my_mock.replay()
+                device = cfg_ds.device_name_to_device(name)
+                self.assertEquals(dev_name, device)
 
     def test_dev_ec2_map(self):
         populate_dir(self.tmp, CFG_DRIVE_FILES_V2)