diff --git a/nose_exclude.py b/nose_exclude.py
index 1fd189e..1f71caa 100644
--- a/nose_exclude.py
+++ b/nose_exclude.py
@@ -21,29 +21,29 @@ class NoseExclude(Plugin):
         """Configure plugin based on command line options"""
         super(NoseExclude, self).configure(options, conf)
 
+        self.exclude_dirs = {}
+
         if not options.exclude_dirs:
             self.enabled = False
             return
-
+        
         self.enabled = True
         root = os.getcwd()
         log.debug('cwd: %s' % root)
 
-        cleaned_dirs = []
+        # Normalize excluded directory names for lookup
         for d in options.exclude_dirs:
             if os.path.isabs(d):
-                cleaned_dirs.append(d)
+                self.exclude_dirs[d] = True
             elif os.path.isdir(d):
                 #see if it's relative
                 new_abs_d = os.path.join(root,d)
-                cleaned_dirs.append(new_abs_d)
+                self.exclude_dirs[new_abs_d] = True
             else:
                 #bad path
                 raise ValueError("invalid path: %s" % d)
 
-        self.exclude_dirs = cleaned_dirs
-
-        exclude_str = "excluding dirs: %s" % ",".join(self.exclude_dirs)
+        exclude_str = "excluding dirs: %s" % ",".join(self.exclude_dirs.keys())
         log.debug(exclude_str)
 
     def wantDirectory(self, dirname):
diff --git a/tests.py b/tests.py
new file mode 100644
index 0000000..e42f559
--- /dev/null
+++ b/tests.py
@@ -0,0 +1,41 @@
+import os
+import unittest
+from nose.plugins import PluginTester
+
+from nose_exclude import NoseExclude
+
+class TestNoseExcludeDirs_Relative_Args(PluginTester, unittest.TestCase):
+
+    exclude_args = "--exclude-dir=test_dirs/build"
+    activate = exclude_args
+    root = os.getcwd()
+    target_arg = os.path.join(root, 'test_dirs')
+    suitepath = target_arg
+    args = ['-vvvv', '--exclude-dir=test_dirs/test_not_me']
+    plugins = [NoseExclude()]
+
+    #def __init__(self, *args, **kwargs):
+    #    super(TestNoseExclude, self).__init__(*args, **kwargs) 
+        
+
+    def test_output(self):
+        assert "FAILED" not in self.output
+
+    def me(self):
+        print self.argv
+        #print self.addargs
+        print "XXXX", self.nose, dir(self.nose)
+        print "test Names", self.nose.testNames
+        print "want", self.nose.__dict__
+        for line in self.output:
+            print "out", line
+
+    #def runTest(self):
+    #    pass
+
+    #def makeSuite(self):
+    #    #return self.target_arg
+    #    return unittest.TestSuite(tests=[TestNoseExclude()])
+
+if __name__ == '__main__':
+    unittest.main()