Merge lp:~allenap/maas/patch-mock-thing into lp:maas/trunk

[Gavin Panella]

Patch-in a MagicMock when no value is specified to TestCase.patch().

[Jeroen T. Vermeulen (jtv)]

Makes sense.

review: Approve

=== modified file 'src/maastesting/testcase.py'
--- src/maastesting/testcase.py	2012-08-24 02:51:42 +0000
+++ src/maastesting/testcase.py	2012-08-24 15:59:19 +0000
@@ -20,6 +20,7 @@
 from fixtures import TempDir
 from maastesting.factory import factory
 from maastesting.scenarios import WithScenarios
+import mock
 from nose.proxy import ResultProxy
 from nose.tools import nottest
 from provisioningserver.testing.worker_cache import WorkerCacheFixture
@@ -121,3 +122,19 @@
     def __call__(self, result=None):
         with active_test(result, self):
             super(TestCase, self).__call__(result)
+
+    def patch(self, obj, attribute, value=mock.sentinel.unset):
+        """Patch `obj.attribute` with `value`.
+
+        If `value` is unspecified, a new `MagicMock` will be created and
+        patched-in instead.
+
+        This is a thin customisation of `testtools.TestCase.patch`, so refer
+        to that in case of doubt.
+
+        :return: The patched-in object.
+        """
+        if value is mock.sentinel.unset:
+            value = mock.MagicMock()
+        super(TestCase, self).patch(obj, attribute, value)
+        return value

=== modified file 'src/maastesting/tests/test_testcase.py'
--- src/maastesting/tests/test_testcase.py	2012-04-20 11:04:42 +0000
+++ src/maastesting/tests/test_testcase.py	2012-08-24 15:59:19 +0000
@@ -16,7 +16,9 @@
 from shutil import rmtree
 from tempfile import mkdtemp
 
+from maastesting.factory import factory
 from maastesting.testcase import TestCase
+from mock import MagicMock
 from testtools.matchers import (
     DirExists,
     FileExists,
@@ -48,3 +50,12 @@
         self.patch(self, 'make_dir', lambda: directory)
         dir_part, file_part = os.path.split(self.make_file())
         self.assertEqual(directory, dir_part)
+
+    def test_patch_can_mock(self):
+        # The patch method patches-in and returns a new MagicMock() instance
+        # if no attribute value is given.
+        attribute_name = factory.make_name("attribute")
+        self.assertRaises(AttributeError, getattr, self, attribute_name)
+        attribute = self.patch(self, attribute_name)
+        self.assertIs(getattr(self, attribute_name), attribute)
+        self.assertIsInstance(attribute, MagicMock)