--- a/configuration/config.py	Mon Mar 26 20:31:12 2012 -0700
+++ b/configuration/config.py	Tue Mar 27 09:30:56 2012 -0700
@@ -4,6 +4,7 @@
 multi-level unified configuration
 """
 
+import copy
 import sys
 import optparse
 
@@ -196,7 +197,14 @@
         """add items to configuration and check it"""
         for config in args:
             self.add(config)
-        self.validate() # validate total configuration
+
+        # add defaults if not present
+        for key, value in self.options.items():
+            if 'default' in value and key not in self.config:
+                self.config[key] = value['default']
+
+        # validate total configuration
+        self.validate()
         # TODO: configuration should be locked after this is called
 
     def add(self, config, check=True):
@@ -268,13 +276,36 @@
             if format in provider.extensions:
                 return provider
 
-    def serialize(self, filename, format=None):
-        """serialize configuration to a file"""
+    def filename2format(self, filename):
+        extension = os.path.splitext(filename)[-1]
+        return extension.rstrip('.') or None
+
+    def serialize(self, filename, format=None, full=False):
+        """
+        serialize configuration to a file
+        - filename: path of file to serialize to
+        - format: format of configuration provider
+        - full: whether to serialize non-set optional strings [TODO]
+        """
         # TODO: allow file object vs file name
 
+        if not format:
+            format = self.filename2format(filename)
+            if not format:
+                raise Exception('Please specify a format')
+                # TODO: more specific exception type
+
+        provider = self.configuration_provider(format)
+
+        config = copy.deepcopy(self.config)
+
+        provider.write(config, filename)
+
     def deserialize(self, filename, format=None):
         """load configuration from a file"""
         # TODO: allow file object vs file name
 
         if not format:
             extension = os.path.splitext(filename)[-1]
+
+        raise NotImplementedError("TODO")

--- a/tests/unit.py	Mon Mar 26 20:31:12 2012 -0700
+++ b/tests/unit.py	Tue Mar 27 09:30:56 2012 -0700
@@ -53,6 +53,11 @@
 
         # serialize to a temporary file
         filename = tempfile.mktemp()
+        config = {'browser_path': '/home/jhammel/bin/firefox',
+                  'activeTests':  ['ts']}
+        example(config)
+        config['test_timeout'] = 1200 # default
+        self.assertEqual(config, example.config)
         if os.path.exists(filename):
             os.remove(filename)