* New fixture ``PythonPathEntry`` which patches sys.path.

  (Robert Collins, #737503)

7 files changed, 109 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index f9ecfb1..b881422 100644
--- a/NEWS
+++ b/NEWS
@@ -6,6 +6,11 @@ fixtures release notes
 IN DEVELOPMENT
 ~~~~~~~~~~~~~~
 
+CHANGES:
+
+* New fixture ``PythonPathEntry`` which patches sys.path.
+  (Robert Collins, #737503)
+
 0.3.5
 ~~~~~
 
diff --git a/README b/README
index c1cc1e8..d2297a4 100644
--- a/README
+++ b/README
@@ -297,9 +297,20 @@ points to Python programs.
 
   >>> fixture = fixtures.PythonPackage('foo.bar', [('quux.py', '')])
 
+PythonPathEntry
++++++++++++++++
+
+Adds a single directory to sys.path. If the directory is already in the path,
+nothing happens, if it isn't then it is added on setUp and removed on cleanUp.
+
+  >>> fixture = fixtures.PythonPathEntry('/foo/bar')
+
 TempDir
 +++++++
 
 Create a temporary directory and clean it up later.
 
   >>> fixture = fixtures.TempDir()
+
+The created directory is stored in the ``path`` attribute of the fixture after
+setUp.
diff --git a/lib/fixtures/__init__.py b/lib/fixtures/__init__.py
index 4a561f2..1729a9e 100644
--- a/lib/fixtures/__init__.py
+++ b/lib/fixtures/__init__.py
@@ -46,6 +46,7 @@ __all__ = [
     'MonkeyPatch',
     'PopenFixture',
     'PythonPackage',
+    'PythonPathEntry',
     'TempDir',
     'TestWithFixtures',
     ]
@@ -57,6 +58,7 @@ from fixtures._fixtures import (
     MonkeyPatch,
     PopenFixture,
     PythonPackage,
+    PythonPathEntry,
     TempDir,
     )
 from fixtures.testcase import TestWithFixtures
diff --git a/lib/fixtures/_fixtures/__init__.py b/lib/fixtures/_fixtures/__init__.py
index fb23907..b18775c 100644
--- a/lib/fixtures/_fixtures/__init__.py
+++ b/lib/fixtures/_fixtures/__init__.py
@@ -21,6 +21,7 @@ __all__ = [
     'MonkeyPatch',
     'PopenFixture',
     'PythonPackage',
+    'PythonPathEntry',
     'TempDir',
     ]
 
@@ -29,4 +30,5 @@ from fixtures._fixtures.environ import EnvironmentVariableFixture
 from fixtures._fixtures.monkeypatch import MonkeyPatch
 from fixtures._fixtures.popen import PopenFixture
 from fixtures._fixtures.pythonpackage import PythonPackage
+from fixtures._fixtures.pythonpath import PythonPathEntry
 from fixtures._fixtures.tempdir import TempDir
diff --git a/lib/fixtures/_fixtures/pythonpath.py b/lib/fixtures/_fixtures/pythonpath.py
new file mode 100644
index 0000000..89c1968
--- /dev/null
+++ b/lib/fixtures/_fixtures/pythonpath.py
@@ -0,0 +1,43 @@
+#  fixtures: Fixtures with cleanups for testing and convenience.
+#
+# Copyright (c) 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__ = [
+    'PythonPathEntry'
+    ]
+
+import sys
+
+from fixtures import Fixture
+
+
+class PythonPathEntry(Fixture):
+    """Add a path to sys.path.
+    
+    If the path is already in sys.path, sys.path will not be altered.
+    """
+
+    def __init__(self, directory):
+        """Create a PythonPathEntry.
+
+        :param directory: The directory to add to sys.path.
+        """
+        self.directory = directory
+
+    def setUp(self):
+        Fixture.setUp(self)
+        if self.directory in sys.path:
+            return
+        self.addCleanup(sys.path.remove, self.directory)
+        sys.path.append(self.directory)
diff --git a/lib/fixtures/tests/_fixtures/__init__.py b/lib/fixtures/tests/_fixtures/__init__.py
index 00b345b..f5dfeef 100644
--- a/lib/fixtures/tests/_fixtures/__init__.py
+++ b/lib/fixtures/tests/_fixtures/__init__.py
@@ -19,6 +19,7 @@ def load_tests(loader, standard_tests, pattern):
         'monkeypatch',
         'popen',
         'pythonpackage',
+        'pythonpath',
         'tempdir',
         ]
     prefix = "fixtures.tests._fixtures.test_"
diff --git a/lib/fixtures/tests/_fixtures/test_pythonpath.py b/lib/fixtures/tests/_fixtures/test_pythonpath.py
new file mode 100644
index 0000000..b0e0281
--- /dev/null
+++ b/lib/fixtures/tests/_fixtures/test_pythonpath.py
@@ -0,0 +1,45 @@
+#  fixtures: Fixtures with cleanups for testing and convenience.
+#
+# Copyright (c) 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.
+
+import sys
+
+import testtools
+
+import fixtures
+from fixtures import (
+    PythonPathEntry,
+    TempDir,
+    )
+
+
+class TestPythonPathEntry(testtools.TestCase):
+
+    def test_adds_missing_to_end_sys_path(self):
+        uniquedir = self.useFixture(TempDir()).path
+        fixture = PythonPathEntry(uniquedir)
+        self.assertFalse(uniquedir in sys.path)
+        with fixture:
+            self.assertTrue(uniquedir in sys.path)
+        self.assertFalse(uniquedir in sys.path)
+
+    def test_doesnt_alter_existing_entry(self):
+        existingdir = sys.path[0]
+        expectedlen = len(sys.path)
+        fixture = PythonPathEntry(existingdir)
+        with fixture:
+            self.assertTrue(existingdir in sys.path)
+            self.assertEqual(expectedlen, len(sys.path))
+        self.assertTrue(existingdir in sys.path)
+        self.assertEqual(expectedlen, len(sys.path))