diff --git a/letsencrypt/client/acme.py b/letsencrypt/client/acme.py
index 52cbceb71..f49cddbb8 100644
--- a/letsencrypt/client/acme.py
+++ b/letsencrypt/client/acme.py
@@ -5,9 +5,9 @@ import pkg_resources
 import jsonschema
 
 
-SCHEMATA = {
-    schema: json.load(open(pkg_resources.resource_filename(
-        __name__, "schemata/%s.json" % schema))) for schema in [
+SCHEMATA = dict([
+    (schema, json.load(open(pkg_resources.resource_filename(
+        __name__, "schemata/%s.json" % schema)))) for schema in [
             "authorization",
             "authorizationRequest",
             "certificate",
@@ -18,32 +18,42 @@ SCHEMATA = {
             "error",
             "revocation",
             "revocationRequest",
-            "statusRequest"
+            "statusRequest",
         ]
-}
+])
 
 
-def acme_object_validate(j):
-    """Validate a JSON object against the ACME protocol using JSON Schema.
+def acme_object_validate(json_string, schemata=None):
+    """Validate a JSON string against the ACME protocol using JSON Schema.
+
+    :param json_string: Well-formed input JSON string.
+    :type json_string: str
+
+    :param schemata: Mapping from type name to JSON Schema definition.
+                     Useful for testing.
+    :type schemata: dict
+
+    :returns: None if validation was successful.
+    :raises: jsonschema.ValidationError if validation was unsuccessful
+             ValueError if the object cannot even be parsed as valid JSON
 
-    Success will return None; failure to validate will raise a
-    jsonschema.ValidationError exception describing the reason that the
-    object could not be validated successfully, or a ValueError exception
-    if the object cannot even be parsed as valid JSON.
     """
-    j = json.loads(j)
-    if not isinstance(j, dict):
+    schemata = SCHEMATA if schemata is None else schemata
+    json_object = json.loads(json_string)
+    if not isinstance(json_object, dict):
         raise jsonschema.ValidationError("this is not a dictionary object")
-    if "type" not in j:
+    if "type" not in json_object:
         raise jsonschema.ValidationError("missing type field")
-    if j["type"] not in SCHEMATA:
-        raise jsonschema.ValidationError("unknown type %s" % j["type"])
-    jsonschema.validate(j, SCHEMATA[j["type"]])
+    if json_object["type"] not in schemata:
+        raise jsonschema.ValidationError(
+            "unknown type %s" % json_object["type"])
+    jsonschema.validate(json_object, schemata[json_object["type"]])
 
 
 def pretty(json_string):
     """Return a pretty-printed version of any JSON string.
 
     Useful when printing out protocol messages for debugging purposes.
+
     """
     return json.dumps(json.loads(json_string), indent=4)
diff --git a/letsencrypt/client/acme_test.py b/letsencrypt/client/acme_test.py
new file mode 100644
index 000000000..e5eae6c9a
--- /dev/null
+++ b/letsencrypt/client/acme_test.py
@@ -0,0 +1,58 @@
+"""Tests for letsencrypt.client.acme."""
+import unittest
+
+import jsonschema
+
+
+class ACMEObjectValidateTest(unittest.TestCase):
+    """Tests for letsencrypt.client.acme.acme_object_validate."""
+
+    def setUp(self):
+        self.schemata = {
+            'foo': {
+                'type' : 'object',
+                'properties' : {
+                    'price' : {'type' : 'number'},
+                    'name' : {'type' : 'string'},
+                },
+            },
+        }
+
+    def _call(self, json_string):
+        from letsencrypt.client.acme import acme_object_validate
+        return acme_object_validate(json_string, self.schemata)
+
+    def _test_fails(self, json_string):
+        self.assertRaises(jsonschema.ValidationError, self._call, json_string)
+
+    def test_non_dictionary_fails(self):
+        self._test_fails('[]')
+
+    def test_dict_without_type_fails(self):
+        self._test_fails('{}')
+
+    def test_unknown_type_fails(self):
+        self._test_fails('{"type": "bar"}')
+
+    def test_valid_returns_none(self):
+        self.assertTrue(self._call('{"type": "foo"}') is None)
+
+    def test_invalid_fails(self):
+        self._test_fails('{"type": "foo", "price": "asd"}')
+
+
+class PrettyTest(unittest.TestCase):
+    """Tests for letsencrypt.client.acme.pretty."""
+
+    def _call(self, json_string):
+        from letsencrypt.client.acme import pretty
+        return pretty(json_string)
+
+    def test_it(self):
+        self.assertEqual(
+            self._call('{"foo": "bar", "foo2": "bar2"}'),
+            '{\n    "foo2": "bar2", \n    "foo": "bar"\n}')
+
+
+if __name__ == '__main__':
+    unittest.main()