1 files changed, 58 insertions, 0 deletions
diff --git a/fixtures/_fixtures/environ.py b/fixtures/_fixtures/environ.py
new file mode 100644
index 0000000..5494429
--- /dev/null
+++ b/fixtures/_fixtures/environ.py
@@ -0,0 +1,58 @@
+#  fixtures: Fixtures with cleanups for testing and convenience.
+#
+# Copyright (c) 2010, 2011, Robert Collins <robertc@robertcollins.net>
+#
+# Licensed under either the Apache License, Version 2.0 or the BSD 3-clause
+# license at the users choice. A copy of both licenses are available in the
+# project source as Apache-2.0 and BSD. You may not use this file except in
+# compliance with one of these two licences.
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under these licenses is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# license you chose for the specific language governing permissions and
+# limitations under that license.
+
+__all__ = [
+    'EnvironmentVariable',
+    'EnvironmentVariableFixture'
+    ]
+
+import os
+
+from fixtures import Fixture
+
+
+class EnvironmentVariable(Fixture):
+    """Isolate a specific environment variable."""
+
+    def __init__(self, varname, newvalue=None):
+        """Create an EnvironmentVariable fixture.
+
+        :param varname: the name of the variable to isolate.
+        :param newvalue: A value to set the variable to. If None, the variable
+            will be deleted.
+
+        During setup the variable will be deleted or assigned the requested
+        value, and this will be restored in cleanUp.
+        """
+        super(EnvironmentVariable, self).__init__()
+        self.varname = varname
+        self.newvalue = newvalue
+
+    def setUp(self):
+        super(EnvironmentVariable, self).setUp()
+        varname = self.varname
+        orig_value = os.environ.get(varname)
+        if orig_value is not None:
+            self.addCleanup(os.environ.__setitem__, varname, orig_value)
+            del os.environ[varname]
+        else:
+            self.addCleanup(os.environ.pop, varname, '')
+        if self.newvalue is not None:
+            os.environ[varname] = self.newvalue
+        else:
+            os.environ.pop(varname, '')
+
+
+EnvironmentVariableFixture = EnvironmentVariable