diff --git a/IPython/nbformat/v3/tests/formattest.py b/IPython/nbformat/v3/tests/formattest.py
new file mode 100644
index 0000000..0aed69a
--- /dev/null
+++ b/IPython/nbformat/v3/tests/formattest.py
@@ -0,0 +1,61 @@
+# -*- coding: utf8 -*-
+import io
+import os
+import shutil
+import tempfile
+
+pjoin = os.path.join
+
+from unittest import TestCase
+
+from ..nbbase import (
+    NotebookNode,
+    new_code_cell, new_text_cell, new_worksheet, new_notebook
+)
+
+from ..nbpy import reads, writes, read, write
+from .nbexamples import nb0, nb0_py
+
+
+class NBFormatTestCase(TestCase):
+
+    # override with appropriate values in subclasses
+    nb0_ref = None
+    ext = None
+    mod = None
+    
+    def setUp(self):
+        self.wd = tempfile.mkdtemp()
+    
+    def tearDown(self):
+        shutil.rmtree(self.wd)
+    
+    def assertNBEquals(self, nba, nbb):
+        self.assertEquals(nba, nbb)
+        
+    def test_writes(self):
+        s = self.mod.writes(nb0)
+        if self.nb0_ref:
+            self.assertEquals(s, self.nb0_ref)
+
+    def test_reads(self):
+        s = self.mod.writes(nb0)
+        nb = self.mod.reads(s)
+
+    def test_roundtrip(self):
+        s = self.mod.writes(nb0)
+        self.assertNBEquals(self.mod.reads(s),nb0)
+
+    def test_write_file(self):
+        with io.open(pjoin(self.wd, "nb0.%s" % self.ext), 'w') as f:
+            self.mod.write(nb0, f)
+    
+    def test_read_file(self):
+        with io.open(pjoin(self.wd, "nb0.%s" % self.ext), 'w') as f:
+            self.mod.write(nb0, f)
+        
+        with io.open(pjoin(self.wd, "nb0.%s" % self.ext), 'r') as f:
+            nb = self.mod.read(f)
+        
+
+        
diff --git a/IPython/nbformat/v3/tests/test_json.py b/IPython/nbformat/v3/tests/test_json.py
index ecbb2d1..5b7d6f8 100644
--- a/IPython/nbformat/v3/tests/test_json.py
+++ b/IPython/nbformat/v3/tests/test_json.py
@@ -2,33 +2,32 @@ import pprint
 from unittest import TestCase
 
 from ..nbjson import reads, writes
+from .. import nbjson
 from .nbexamples import nb0
 
+from . import formattest
 
-class TestJSON(TestCase):
+from .nbexamples import nb0
+
+
+class TestJSON(formattest.NBFormatTestCase):
+
+    nb0_ref = None
+    ext = 'ipynb'
+    mod = nbjson
 
-    def test_roundtrip(self):
-        s = writes(nb0)
-        # print
-        # print pprint.pformat(nb0,indent=2)
-        # print
-        # print pprint.pformat(reads(s),indent=2)
-        # print
-        # print s
-        self.assertEquals(reads(s),nb0)
-    
     def test_roundtrip_nosplit(self):
         """Ensure that multiline blobs are still readable"""
         # ensures that notebooks written prior to splitlines change
         # are still readable.
         s = writes(nb0, split_lines=False)
-        self.assertEquals(reads(s),nb0)
+        self.assertEquals(nbjson.reads(s),nb0)
 
     def test_roundtrip_split(self):
         """Ensure that splitting multiline blocks is safe"""
         # This won't differ from test_roundtrip unless the default changes
         s = writes(nb0, split_lines=True)
-        self.assertEquals(reads(s),nb0)
+        self.assertEquals(nbjson.reads(s),nb0)
 
 
 
diff --git a/IPython/nbformat/v3/tests/test_nbpy.py b/IPython/nbformat/v3/tests/test_nbpy.py
index 4c12c4e..ca8f56b 100644
--- a/IPython/nbformat/v3/tests/test_nbpy.py
+++ b/IPython/nbformat/v3/tests/test_nbpy.py
@@ -1,17 +1,38 @@
-from unittest import TestCase
+# -*- coding: utf8 -*-
+from . import formattest
 
-from ..nbbase import (
-    NotebookNode,
-    new_code_cell, new_text_cell, new_worksheet, new_notebook
-)
-
-from ..nbpy import reads, writes
+from .. import nbpy
 from .nbexamples import nb0, nb0_py
 
 
-class TestPy(TestCase):
+class TestPy(formattest.NBFormatTestCase):
 
-    def test_write(self):
-        s = writes(nb0)
-        self.assertEquals(s,nb0_py)
+    nb0_ref = nb0_py
+    ext = 'py'
+    mod = nbpy
+    ignored_keys = ['collapsed', 'outputs', 'prompt_number', 'metadata']
 
+    def assertSubset(self, da, db):
+        """assert that da is a subset of db, ignoring self.ignored_keys.
+        
+        Called recursively on containers, ultimately comparing individual
+        elements.
+        """
+        if isinstance(da, dict):
+            for k,v in da.iteritems():
+                if k in self.ignored_keys:
+                    continue
+                self.assertTrue(k in db)
+                self.assertSubset(v, db[k])
+        elif isinstance(da, list):
+            for a,b in zip(da, db):
+                self.assertSubset(a,b)
+        else:
+            self.assertEquals(da, db)
+        return True
+    
+    def assertNBEquals(self, nba, nbb):
+        # since roundtrip is lossy, only compare keys that are preserved
+        # assumes nba is read from my file format
+        return self.assertSubset(nba, nbb)
+