diff --git a/Makefile b/Makefile
index efc50dc..fb75c08 100644
--- a/Makefile
+++ b/Makefile
@@ -82,11 +82,11 @@
 	PYTHONPATH=. ./utest/test_test_data.py
 
 check-py: python
-	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi python py_gen/tests/generic_util.py
-	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi python py_gen/tests/of10.py
-	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi python py_gen/tests/of11.py
-	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi python py_gen/tests/of12.py
-	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi python py_gen/tests/of13.py
+	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi:. python py_gen/tests/generic_util.py
+	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi:. python py_gen/tests/of10.py
+	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi:. python py_gen/tests/of11.py
+	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi:. python py_gen/tests/of12.py
+	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi:. python py_gen/tests/of13.py
 
 pylint:
 	pylint -E ${LOXI_PY_FILES}
diff --git a/py_gen/tests/of10.py b/py_gen/tests/of10.py
index 79049a5..fa97a79 100644
--- a/py_gen/tests/of10.py
+++ b/py_gen/tests/of10.py
@@ -26,6 +26,8 @@
 # EPL for the specific language governing permissions and limitations
 # under the EPL.
 import unittest
+import test_data
+from testutil import test_datafile
 
 try:
     import loxi.of10 as ofp
@@ -56,22 +58,8 @@
         self.assertTrue(hasattr(loxi.of10, "message"))
 
 class TestActions(unittest.TestCase):
-    def test_output_pack(self):
-        expected = "\x00\x00\x00\x08\xff\xf8\xff\xff"
-        action = ofp.action.output(port=ofp.OFPP_IN_PORT, max_len=0xffff)
-        self.assertEquals(expected, action.pack())
-
-    def test_output_unpack(self):
-        # Normal case
-        buf = "\x00\x00\x00\x08\xff\xf8\xff\xff"
-        action = ofp.action.output.unpack(buf)
-        self.assertEqual(action.port, ofp.OFPP_IN_PORT)
-        self.assertEqual(action.max_len, 0xffff)
-
-        # Invalid length
-        #buf = "\x00\x00\x00\x09\xff\xf8\xff\xff\x00"
-        #with self.assertRaises(ofp.ProtocolError):
-        #    ofp.action.output.unpack(buf)
+    def test_output(self):
+        test_datafile('action_output.data')
 
     def test_output_equality(self):
         action = ofp.action.output(port=1, max_len=0x1234)
@@ -86,31 +74,8 @@
         self.assertNotEquals(action, action2)
         action2.max_len = 0x1234
 
-    def test_output_show(self):
-        action = ofp.action.output(port=1, max_len=0x1234)
-        expected = "output { port = 1, max_len = 0x1234 }"
-        self.assertEquals(expected, action.show())
-
-    def test_bsn_set_tunnel_dst_pack(self):
-        expected = ''.join([
-            "\xff\xff", "\x00\x10", # type/length
-            "\x00\x5c\x16\xc7", # experimenter
-            "\x00\x00\x00\x02", # subtype
-            "\x12\x34\x56\x78" # dst
-        ])
-        action = ofp.action.bsn_set_tunnel_dst(dst=0x12345678)
-        self.assertEquals(expected, action.pack())
-
-    def test_bsn_set_tunnel_dst_unpack(self):
-        buf = ''.join([
-            "\xff\xff", "\x00\x10", # type/length
-            "\x00\x5c\x16\xc7", # experimenter
-            "\x00\x00\x00\x02", # subtype
-            "\x12\x34\x56\x78" # dst
-        ])
-        action = ofp.action.bsn_set_tunnel_dst.unpack(buf)
-        self.assertEqual(action.subtype, 2)
-        self.assertEqual(action.dst, 0x12345678)
+    def test_bsn_set_tunnel_dst(self):
+        test_datafile('of10/action_bsn_set_tunnel_dst.data')
 
 # Assumes action serialization/deserialization works
 class TestActionList(unittest.TestCase):
@@ -165,152 +130,14 @@
         self.assertEquals(0xfc000, ofp.OFPFW_NW_DST_MASK)
 
 class TestCommon(unittest.TestCase):
-    def test_port_desc_pack(self):
-        obj = ofp.port_desc(port_no=ofp.OFPP_CONTROLLER,
-                            hw_addr=[1,2,3,4,5,6],
-                            name="foo",
-                            config=ofp.OFPPC_NO_FLOOD,
-                            state=ofp.OFPPS_STP_FORWARD,
-                            curr=ofp.OFPPF_10MB_HD,
-                            advertised=ofp.OFPPF_1GB_FD,
-                            supported=ofp.OFPPF_AUTONEG,
-                            peer=ofp.OFPPF_PAUSE_ASYM)
-        expected = ''.join([
-            '\xff\xfd', # port_no
-            '\x01\x02\x03\x04\x05\x06', # hw_addr
-            'foo'.ljust(16, '\x00'), # name
-            '\x00\x00\x00\x10', # config
-            '\x00\x00\x02\x00', # state
-            '\x00\x00\x00\x01', # curr
-            '\x00\x00\x00\x20', # advertised
-            '\x00\x00\x02\x00', # supported
-            '\x00\x00\x08\x00', # peer
-        ])
-        self.assertEquals(expected, obj.pack())
+    def test_port_desc(self):
+        test_datafile('of10/port_desc.data')
 
-    def test_port_desc_unpack(self):
-        buf = ''.join([
-            '\xff\xfd', # port_no
-            '\x01\x02\x03\x04\x05\x06', # hw_addr
-            'foo'.ljust(16, '\x00'), # name
-            '\x00\x00\x00\x10', # config
-            '\x00\x00\x02\x00', # state
-            '\x00\x00\x00\x01', # curr
-            '\x00\x00\x00\x20', # advertised
-            '\x00\x00\x02\x00', # supported
-            '\x00\x00\x08\x00', # peer
-        ])
-        obj = ofp.port_desc.unpack(buf)
-        self.assertEquals(ofp.OFPP_CONTROLLER, obj.port_no)
-        self.assertEquals('foo', obj.name)
-        self.assertEquals(ofp.OFPPF_PAUSE_ASYM, obj.peer)
+    def test_table_stats_entry(self):
+        test_datafile('of10/table_stats_entry.data')
 
-    def test_table_stats_entry_pack(self):
-        obj = ofp.table_stats_entry(table_id=3,
-                                    name="foo",
-                                    wildcards=ofp.OFPFW_ALL,
-                                    max_entries=5,
-                                    active_count=2,
-                                    lookup_count=1099511627775,
-                                    matched_count=9300233470495232273L)
-        expected = ''.join([
-            '\x03', # table_id
-            '\x00\x00\x00', # pad
-            'foo'.ljust(32, '\x00'), # name
-            '\x00\x3f\xFF\xFF', # wildcards
-            '\x00\x00\x00\x05', # max_entries
-            '\x00\x00\x00\x02', # active_count
-            '\x00\x00\x00\xff\xff\xff\xff\xff', # lookup_count
-            '\x81\x11\x11\x11\x11\x11\x11\x11', # matched_count
-        ])
-        self.assertEquals(expected, obj.pack())
-
-    def test_table_stats_entry_unpack(self):
-        buf = ''.join([
-            '\x03', # table_id
-            '\x00\x00\x00', # pad
-            'foo'.ljust(32, '\x00'), # name
-            '\x00\x3f\xFF\xFF', # wildcards
-            '\x00\x00\x00\x05', # max_entries
-            '\x00\x00\x00\x02', # active_count
-            '\x00\x00\x00\xff\xff\xff\xff\xff', # lookup_count
-            '\x81\x11\x11\x11\x11\x11\x11\x11', # matched_count
-        ])
-        obj = ofp.table_stats_entry.unpack(buf)
-        self.assertEquals(3, obj.table_id)
-        self.assertEquals('foo', obj.name)
-        self.assertEquals(9300233470495232273L, obj.matched_count)
-
-    def test_flow_stats_entry_pack(self):
-        obj = ofp.flow_stats_entry(table_id=3,
-                                   match=ofp.match(),
-                                   duration_sec=1,
-                                   duration_nsec=2,
-                                   priority=100,
-                                   idle_timeout=5,
-                                   hard_timeout=10,
-                                   cookie=0x0123456789abcdef,
-                                   packet_count=10,
-                                   byte_count=1000,
-                                   actions=[ofp.action.output(port=1),
-                                            ofp.action.output(port=2)])
-        expected = ''.join([
-            '\x00\x68', # length
-            '\x03', # table_id
-            '\x00', # pad
-            '\x00\x3f\xff\xff', # match.wildcards
-            '\x00' * 36, # remaining match fields
-            '\x00\x00\x00\x01', # duration_sec
-            '\x00\x00\x00\x02', # duration_nsec
-            '\x00\x64', # priority
-            '\x00\x05', # idle_timeout
-            '\x00\x0a', # hard_timeout
-            '\x00' * 6, # pad2
-            '\x01\x23\x45\x67\x89\xab\xcd\xef', # cookie
-            '\x00\x00\x00\x00\x00\x00\x00\x0a', # packet_count
-            '\x00\x00\x00\x00\x00\x00\x03\xe8', # byte_count
-            '\x00\x00', # actions[0].type
-            '\x00\x08', # actions[0].len
-            '\x00\x01', # actions[0].port
-            '\x00\x00', # actions[0].max_len
-            '\x00\x00', # actions[1].type
-            '\x00\x08', # actions[1].len
-            '\x00\x02', # actions[1].port
-            '\x00\x00', # actions[1].max_len
-        ])
-        self.assertEquals(expected, obj.pack())
-
-    def test_flow_stats_entry_unpack(self):
-        buf = ''.join([
-            '\x00\x68', # length
-            '\x03', # table_id
-            '\x00', # pad
-            '\x00\x3f\xff\xff', # match.wildcards
-            '\x00' * 36, # remaining match fields
-            '\x00\x00\x00\x01', # duration_sec
-            '\x00\x00\x00\x02', # duration_nsec
-            '\x00\x64', # priority
-            '\x00\x05', # idle_timeout
-            '\x00\x0a', # hard_timeout
-            '\x00' * 6, # pad2
-            '\x01\x23\x45\x67\x89\xab\xcd\xef', # cookie
-            '\x00\x00\x00\x00\x00\x00\x00\x0a', # packet_count
-            '\x00\x00\x00\x00\x00\x00\x03\xe8', # byte_count
-            '\x00\x00', # actions[0].type
-            '\x00\x08', # actions[0].len
-            '\x00\x01', # actions[0].port
-            '\x00\x00', # actions[0].max_len
-            '\x00\x00', # actions[1].type
-            '\x00\x08', # actions[1].len
-            '\x00\x02', # actions[1].port
-            '\x00\x00', # actions[1].max_len
-        ])
-        obj = ofp.flow_stats_entry.unpack(buf)
-        self.assertEquals(3, obj.table_id)
-        self.assertEquals(ofp.OFPFW_ALL, obj.match.wildcards)
-        self.assertEquals(2, len(obj.actions))
-        self.assertEquals(1, obj.actions[0].port)
-        self.assertEquals(2, obj.actions[1].port)
+    def test_flow_stats_entry(self):
+        test_datafile('of10/flow_stats_entry.data')
 
     def test_match(self):
         match = ofp.match()
@@ -334,34 +161,15 @@
         msg = ofp.message.hello(xid=0)
         self.assertEquals(msg.xid, 0)
 
-    def test_hello_unpack(self):
-        # Normal case
-        buf = "\x01\x00\x00\x08\x12\x34\x56\x78"
-        msg = ofp.message.hello(xid=0x12345678)
-        self.assertEquals(buf, msg.pack())
-
-        # Invalid length
-        #buf = "\x01\x00\x00\x09\x12\x34\x56\x78\x9a"
-        #with self.assertRaisesRegexp(ofp.ProtocolError, "should be 8"):
-        #    ofp.message.hello.unpack(buf)
+    def test_hello(self):
+        test_datafile('of10/hello.data')
 
     def test_echo_request_construction(self):
         msg = ofp.message.echo_request(data="abc")
         self.assertEquals(msg.data, "abc")
 
-    def test_echo_request_pack(self):
-        msg = ofp.message.echo_request(xid=0x12345678, data="abc")
-        buf = msg.pack()
-        self.assertEquals(buf, "\x01\x02\x00\x0b\x12\x34\x56\x78\x61\x62\x63")
-
-        msg2 = ofp.message.echo_request.unpack(buf)
-        self.assertEquals(msg, msg2)
-
-    def test_echo_request_unpack(self):
-        # Normal case
-        buf = "\x01\x02\x00\x0b\x12\x34\x56\x78\x61\x62\x63"
-        msg = ofp.message.echo_request(xid=0x12345678, data="abc")
-        self.assertEquals(buf, msg.pack())
+    def test_echo_request(self):
+        test_datafile('of10/echo_request.data')
 
         # Invalid length
         buf = "\x01\x02\x00\x07\x12\x34\x56"
@@ -382,11 +190,6 @@
         self.assertNotEquals(msg, msg2)
         msg2.data = msg.data
 
-    def test_echo_request_show(self):
-        expected = "echo_request { xid = 0x12345678, data = 'ab\\x01' }"
-        msg = ofp.message.echo_request(xid=0x12345678, data="ab\x01")
-        self.assertEquals(msg.show(), expected)
-
     def test_flow_add(self):
         match = ofp.match()
         msg = ofp.message.flow_add(xid=1,
diff --git a/py_gen/tests/testutil.py b/py_gen/tests/testutil.py
index 6ca0b7c..0642c2a 100644
--- a/py_gen/tests/testutil.py
+++ b/py_gen/tests/testutil.py
@@ -26,7 +26,9 @@
 # EPL for the specific language governing permissions and limitations
 # under the EPL.
 
+import sys
 import difflib
+import test_data
 
 # Human-friendly format for binary strings. 8 bytes per line.
 def format_binary(buf):
@@ -56,3 +58,20 @@
         b = unpacked.show()
         raise AssertionError("Deserialization of %s failed\nExpected:\n%s\nActual:\n%s\nDiff:\n%s" % \
             (type(obj).__name__, a, b, diff(a, b)))
+
+def test_pretty(obj, expected):
+    pretty = obj.show()
+    if expected != pretty:
+        raise AssertionError("Pretty printing of %s failed\nExpected:\n%s\nActual:\n%s\nDiff:\n%s" % \
+            (type(obj).__name__, expected, pretty, diff(expected, pretty)))
+
+# Run test_serialization and possibly test_pretty against the named data file
+# Uses the globals of the calling function to get 'ofp'
+def test_datafile(name):
+    data = test_data.read(name)
+    binary = data['binary']
+    python = data['python']
+    obj = eval(python, sys._getframe(1).f_globals)
+    test_serialization(obj, binary)
+    if 'python pretty-printer' in data:
+        test_pretty(obj, data['python pretty-printer'])
diff --git a/test_data/action_output.data b/test_data/action_output.data
new file mode 100644
index 0000000..3afb525
--- /dev/null
+++ b/test_data/action_output.data
@@ -0,0 +1,9 @@
+-- binary
+00 00 # type
+00 08 # len
+ff f8 # in_port
+ff ff # max_len
+-- python
+ofp.action.output(port=ofp.OFPP_IN_PORT, max_len=0xffff)
+-- python pretty-printer
+output { port = OFPP_IN_PORT, max_len = 0xffff }
diff --git a/test_data/of10/action_bsn_set_tunnel_dst.data b/test_data/of10/action_bsn_set_tunnel_dst.data
new file mode 100644
index 0000000..7e1f43d
--- /dev/null
+++ b/test_data/of10/action_bsn_set_tunnel_dst.data
@@ -0,0 +1,10 @@
+-- binary
+ff ff # type
+00 10 # len
+00 5c 16 c7 # experimenter
+00 00 00 02 # subtype
+12 34 56 78 # dst
+-- python
+ofp.action.bsn_set_tunnel_dst(dst=0x12345678)
+-- python pretty-printer
+bsn_set_tunnel_dst { dst = 0x12345678 }
diff --git a/test_data/of10/echo_request.data b/test_data/of10/echo_request.data
new file mode 100644
index 0000000..abe06fc
--- /dev/null
+++ b/test_data/of10/echo_request.data
@@ -0,0 +1,9 @@
+-- binary
+01 02 # version / type
+00 0b # length
+12 34 56 78 # xid
+61 62 01 # data
+-- python
+ofp.message.echo_request(xid=0x12345678, data="ab\x01")
+-- python pretty-printer
+echo_request { xid = 0x12345678, data = 'ab\x01' }
diff --git a/test_data/of10/flow_stats_entry.data b/test_data/of10/flow_stats_entry.data
new file mode 100644
index 0000000..45c6569
--- /dev/null
+++ b/test_data/of10/flow_stats_entry.data
@@ -0,0 +1,42 @@
+-- binary
+00 68 # length
+03 # table_id
+00 # pad
+00 3f ff ff # match.wildcards
+00 00 00 00 # remaining match fields
+00 00 00 00 00 00 00 00 # ...
+00 00 00 00 00 00 00 00 # ...
+00 00 00 00 00 00 00 00 # ...
+00 00 00 00 00 00 00 00 # ...
+00 00 00 01 # duration_sec
+00 00 00 02 # duration_nsec
+00 64 # priority
+00 05 # idle_timeout
+00 0a # hard_timeout
+00 00 00 00 00 00 # pad
+01 23 45 67 89 ab cd ef # cookie
+00 00 00 00 00 00 00 0a # packet_count
+00 00 00 00 00 00 03 e8 # byte_count
+00 00 # actions[0].type
+00 08 # actions[0].len
+00 01 # actions[0].port
+00 00 # actions[0].max_len
+00 00 # actions[1].type
+00 08 # actions[1].len
+00 02 # actions[1].port
+00 00 # actions[1].max_len
+-- python
+ofp.flow_stats_entry(
+    table_id=3,
+    match=ofp.match(),
+    duration_sec=1,
+    duration_nsec=2,
+    priority=100,
+    idle_timeout=5,
+    hard_timeout=10,
+    cookie=0x0123456789abcdef,
+    packet_count=10,
+    byte_count=1000,
+    actions=[
+        ofp.action.output(port=1),
+        ofp.action.output(port=2)])
diff --git a/test_data/of10/hello.data b/test_data/of10/hello.data
new file mode 100644
index 0000000..2603365
--- /dev/null
+++ b/test_data/of10/hello.data
@@ -0,0 +1,6 @@
+-- binary
+01 00 # version / type
+00 08 # length
+12 34 56 78 # xid
+-- python
+ofp.message.hello(xid=0x12345678)
diff --git a/test_data/of10/port_desc.data b/test_data/of10/port_desc.data
new file mode 100644
index 0000000..c3c2e38
--- /dev/null
+++ b/test_data/of10/port_desc.data
@@ -0,0 +1,21 @@
+-- binary
+ff fd # port_no
+01 02 03 04 05 06 # hw_addr
+66 6f 6f 00 00 00 00 00 00 00 00 00 00 00 00 00 # name
+00 00 00 10 # config
+00 00 02 00 # state
+00 00 00 01 # curr
+00 00 00 20 # advertised
+00 00 02 00 # supported
+00 00 08 00 # peer
+-- python
+ofp.port_desc(
+    port_no=ofp.OFPP_CONTROLLER,
+    hw_addr=[1,2,3,4,5,6],
+    name="foo",
+    config=ofp.OFPPC_NO_FLOOD,
+    state=ofp.OFPPS_STP_FORWARD,
+    curr=ofp.OFPPF_10MB_HD,
+    advertised=ofp.OFPPF_1GB_FD,
+    supported=ofp.OFPPF_AUTONEG,
+    peer=ofp.OFPPF_PAUSE_ASYM)
diff --git a/test_data/of10/table_stats_entry.data b/test_data/of10/table_stats_entry.data
new file mode 100644
index 0000000..1a99237
--- /dev/null
+++ b/test_data/of10/table_stats_entry.data
@@ -0,0 +1,21 @@
+-- binary
+03 # table_id
+00 00 00 # pad
+66 6f 6f 00 00 00 00 00 # name
+00 00 00 00 00 00 00 00 # name
+00 00 00 00 00 00 00 00 # name
+00 00 00 00 00 00 00 00 # name
+00 3f ff ff # wildcards
+00 00 00 05 # max_entries
+00 00 00 02 # active_count
+00 00 00 ff ff ff ff ff # lookup_count
+81 11 11 11 11 11 11 11 # matched_count
+-- python
+ofp.table_stats_entry(
+    table_id=3,
+    name="foo",
+    wildcards=ofp.OFPFW_ALL,
+    max_entries=5,
+    active_count=2,
+    lookup_count=1099511627775,
+    matched_count=9300233470495232273L)