add tests for registering serializer

tests/integration/test_register_serializer.py

@@ -0,0 +1,33 @@
+import urllib2
+import vcr
+
+class MockSerializer(object):
+    def __init__(self):
+        self.serialize_count = 0
+        self.deserialize_count = 0
+        self.load_args = None
+
+    def deserialize(self, cassette_string):
+        self.serialize_count += 1
+        self.cassette_string = cassette_string
+        return ([], [])
+
+    def serialize(self, cassette_dict):
+        self.deserialize_count += 1
+        return ""
+
+def test_registered_serializer(tmpdir):
+    ms = MockSerializer()
+    my_vcr = vcr.VCR()
+    my_vcr.register_serializer('mock', ms)
+    tmpdir.join('test.mock').write('test_data')
+    with my_vcr.use_cassette(str(tmpdir.join('test.mock')), serializer='mock'):
+        urllib2.urlopen('http://httpbin.org/')
+        assert ms.serialize_count == 1 # Serializer deserialized once
+        assert ms.cassette_string == 'test_data' # and serialized the test data string
+        assert ms.deserialize_count == 0 # and hasn't serialized yet
+
+    assert ms.serialize_count == 1
+
+
+