Add test helper to set temporary value

qutebrowser/test/helpers.py

@@ -0,0 +1,35 @@
+# Copyright 2014 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
+#
+# This file is part of qutebrowser.
+#
+# qutebrowser is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# qutebrowser is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Helpers needed by tests."""
+
+import os
+from contextlib import contextmanager
+
+@contextmanager
+def environ_set_temp(name, value):
+    """Set a temporary environment variable."""
+    try:
+        oldval = os.environ[name]
+    except KeyError:
+        oldval = None
+    os.environ[name] = value
+    yield
+    if oldval is not None:
+        os.environ[name] = oldval
+    else:
+        del os.environ[name]

qutebrowser/test/test_helpers.py

@@ -0,0 +1,42 @@
+# Copyright 2014 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
+#
+# This file is part of qutebrowser.
+#
+# qutebrowser is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# qutebrowser is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Test test helpers."""
+
+import os
+import unittest
+from unittest import TestCase
+
+from qutebrowser.test.helpers import environ_set_temp
+
+class TestEnvironSetTemp(TestCase):
+
+    def test_environ_set(self):
+        os.environ['QUTEBROWSER_ENVIRON_TEST'] = 'oldval'
+        with environ_set_temp('QUTEBROWSER_ENVIRON_TEST', 'newval'):
+            self.assertEqual(os.environ['QUTEBROWSER_ENVIRON_TEST'], 'newval')
+        self.assertEqual(os.environ['QUTEBROWSER_ENVIRON_TEST'], 'oldval')
+
+    def test_environ_unset(self):
+        with environ_set_temp('QUTEBROWSER_ENVIRON_TEST', 'newval'):
+            self.assertEqual(os.environ['QUTEBROWSER_ENVIRON_TEST'], 'newval')
+        self.assertNotIn('QUTEBROWSER_ENVIRON_TEST', os.environ)
+
+    def tearDown(self):
+        if 'QUTEBROWSER_ENVIRON_TEST' in os.environ:
+            # if some test failed
+            del os.environ['QUTEBROWSER_ENVIRON_TEST']