Add a fixture to let tests manage the lazy flag

We do not want to expose the stored lazy flag, but we do want to allow
applications to force it to a certain state and then restore it to its
original test for testing. This new fixture provides a way to do that.

Change-Id: Ica05fd8fc7e687da69d61ea84bf1ceae65db93ce

oslo_i18n/fixture.py

@@ -16,6 +16,7 @@
 import fixtures
 import six
 
+from oslo_i18n import _lazy
 from oslo_i18n import _message
 
 
@@ -63,3 +64,26 @@ class Translation(fixtures.Fixture):
 
         """
         return six.text_type(msg)
+
+
+class ToggleLazy(fixtures.Fixture):
+    """Fixture to toggle lazy translation on or off for a test."""
+
+    def __init__(self, enabled):
+        """Force lazy translation on or off.
+
+        :param enabled: Flag controlling whether to enable or disable
+            lazy translation, passed to :func:`~oslo_i18n.enable_lazy`.
+        :type enabled: bool
+        """
+        super(ToggleLazy, self).__init__()
+        self._enabled = enabled
+        self._original_value = _lazy.USE_LAZY
+
+    def setUp(self):
+        super(ToggleLazy, self).setUp()
+        self.addCleanup(self._restore_original)
+        _lazy.enable_lazy(self._enabled)
+
+    def _restore_original(self):
+        _lazy.enable_lazy(self._original_value)

oslo_i18n/tests/test_fixture.py

@@ -15,14 +15,15 @@
 from oslotest import base as test_base
 import six
 
+from oslo_i18n import _lazy
 from oslo_i18n import _message
 from oslo_i18n import fixture
 
 
-class FixtureTest(test_base.BaseTestCase):
+class TranslationFixtureTest(test_base.BaseTestCase):
 
     def setUp(self):
-        super(FixtureTest, self).setUp()
+        super(TranslationFixtureTest, self).setUp()
         self.trans_fixture = self.useFixture(fixture.Translation())
 
     def test_lazy(self):
@@ -36,3 +37,38 @@ class FixtureTest(test_base.BaseTestCase):
         self.assertFalse(isinstance(msg, _message.Message))
         self.assertIsInstance(msg, six.text_type)
         self.assertEqual(msg, u'this is a lazy message')
+
+
+class ToggleLazyFixtureText(test_base.BaseTestCase):
+
+    def test_on_on(self):
+        _lazy.USE_LAZY = True
+        f = fixture.ToggleLazy(True)
+        f.setUp()
+        self.assertTrue(_lazy.USE_LAZY)
+        f._restore_original()
+        self.assertTrue(_lazy.USE_LAZY)
+
+    def test_on_off(self):
+        _lazy.USE_LAZY = True
+        f = fixture.ToggleLazy(False)
+        f.setUp()
+        self.assertFalse(_lazy.USE_LAZY)
+        f._restore_original()
+        self.assertTrue(_lazy.USE_LAZY)
+
+    def test_off_on(self):
+        _lazy.USE_LAZY = False
+        f = fixture.ToggleLazy(True)
+        f.setUp()
+        self.assertTrue(_lazy.USE_LAZY)
+        f._restore_original()
+        self.assertFalse(_lazy.USE_LAZY)
+
+    def test_off_off(self):
+        _lazy.USE_LAZY = False
+        f = fixture.ToggleLazy(False)
+        f.setUp()
+        self.assertFalse(_lazy.USE_LAZY)
+        f._restore_original()
+        self.assertFalse(_lazy.USE_LAZY)