Add SpawnFixture

This just turns spawn_n into a blocking passthrough so that we actually
run the spawned thing synchronously instead of not running it (and often
thinking we did).

Change-Id: I47ce83505361084e262843505031e3327d8e68a8

nova/tests/fixtures.py

@@ -402,3 +402,12 @@ class IndirectionAPIFixture(fixtures.Fixture):
         self.orig_indirection_api = obj_base.NovaObject.indirection_api
         obj_base.NovaObject.indirection_api = self.indirection_api
         self.addCleanup(self.cleanup)
+
+
+class SpawnIsSynchronousFixture(fixtures.Fixture):
+    """Patch and restore the spawn_n utility method to be synchronous"""
+
+    def setUp(self):
+        super(SpawnIsSynchronousFixture, self).setUp()
+        self.useFixture(fixtures.MonkeyPatch(
+            'nova.utils.spawn_n', lambda f, *a, **k: f(*a, **k)))

nova/tests/unit/test_fixtures.py

@@ -17,6 +17,7 @@
 import sys
 
 import fixtures as fx
+import mock
 from oslo_config import cfg
 from oslo_log import log as logging
 from oslo_utils import uuidutils
@@ -26,6 +27,7 @@ from nova.db.sqlalchemy import api as session
 from nova.objects import base as obj_base
 from nova.tests import fixtures
 from nova.tests.unit import conf_fixture
+from nova import utils
 
 CONF = cfg.CONF
 
@@ -292,3 +294,18 @@ class TestIndirectionAPIFixture(testtools.TestCase):
 
         # ensure the initial value is restored
         self.assertIsNone(obj_base.NovaObject.indirection_api)
+
+
+class TestSpawnIsSynchronousFixture(testtools.TestCase):
+    def test_spawn_patch(self):
+        orig_spawn = utils.spawn_n
+
+        fix = fixtures.SpawnIsSynchronousFixture()
+        self.useFixture(fix)
+        self.assertNotEqual(orig_spawn, utils.spawn_n)
+
+    def test_spawn_passes_through(self):
+        self.useFixture(fixtures.SpawnIsSynchronousFixture())
+        tester = mock.MagicMock()
+        utils.spawn_n(tester.function, 'foo', bar='bar')
+        tester.function.assert_called_once_with('foo', bar='bar')