Add common FileConfigTestCase class, in new testing module

hoping i do not regret this decision..  since the tests do not live in
a "real" package i think the only way to share code is to add some
things to the main package

tests/test_conf.py

@@ -2,8 +2,6 @@
 
 import configparser
 import os
-import shutil
-import tempfile
 from unittest import TestCase
 from unittest.mock import patch, MagicMock
 
@@ -13,21 +11,10 @@ from wuttjamaican import conf
 from wuttjamaican.exc import ConfigurationError
 from wuttjamaican.db import Session
 from wuttjamaican.app import AppHandler
+from wuttjamaican.testing import FileConfigTestCase
 
 
-class TestWuttaConfig(TestCase):
-
-    def setUp(self):
-        self.tempdir = tempfile.mkdtemp()
-
-    def tearDown(self):
-        shutil.rmtree(self.tempdir)
-
-    def write_file(self, filename, content):
-        path = os.path.join(self.tempdir, filename)
-        with open(path, 'wt') as f:
-            f.write(content)
-        return path
+class TestWuttaConfig(FileConfigTestCase):
 
     def test_contstructor_basic(self):
         config = conf.WuttaConfig()
@@ -430,24 +417,12 @@ class TestGenericDefaultFiles(TestCase):
                 self.assertEqual(len(files), 0)
 
 
-class TestMakeConfig(TestCase):
+class TestMakeConfig(FileConfigTestCase):
 
     # nb. we use appname='wuttatest' in this suite to avoid any
     # "valid" default config files, env vars etc. which may be present
     # on the dev machine
 
-    def setUp(self):
-        self.tempdir = tempfile.mkdtemp()
-
-    def tearDown(self):
-        shutil.rmtree(self.tempdir)
-
-    def write_file(self, filename, content):
-        path = os.path.join(self.tempdir, filename)
-        with open(path, 'wt') as f:
-            f.write(content)
-        return path
-
     def test_generic_default_files(self):
         generic = self.write_file('generic.conf', '')