diff --git a/google/refine.py b/google/refine.py
index b88f299..32fa920 100644
--- a/google/refine.py
+++ b/google/refine.py
@@ -179,7 +179,9 @@ class RefineServer(object):
         """Open a Refine URL, optionally POST data, and return parsed JSON."""
         response = json.loads(self.urlopen(*args, **kwargs).read())
         if 'code' in response and response['code'] != 'ok':
-            raise Exception(response['code'] + ': ' + response['message'])
+            raise Exception(
+                response['code'] + ': ' +
+                response.get('message', response.get('stack', response)))
         return response
 
 
@@ -415,3 +417,34 @@ class RefineProject:
             'engine': self.engine.as_json(), 'columnName': column,
             'expression': expression, 'edits': edits})
         return response
+
+    clusterer_defaults = {
+        'binning': {
+            'type': 'binning',
+            'function': 'fingerprint',
+            'params': {},
+        },
+        'knn': {
+            'type': 'knn',
+            'function': 'levenshtein',
+            'params': {
+                'radius': 1,
+                'blocking-ngram-size': 6,
+            },
+        },
+    }
+    def compute_clusters(self, column, clusterer_type='binning',
+                         function=None, params=None):
+        """Returns a list of clusters of {'value': ..., 'count': ...}."""
+        clusterer = self.clusterer_defaults[clusterer_type]
+        if params is not None:
+            clusterer['params'] = params
+        if function is not None:
+            clusterer['function'] = function
+        clusterer['column'] = column
+        response = self.do_json('compute-clusters', {
+            'engine': self.engine.as_json(),
+            'clusterer': json.dumps(clusterer)})
+        return [[{'value': x['v'], 'count': x['c']} for x in cluster]
+                for cluster in response]
+
diff --git a/google/test/test_refine.py b/google/test/test_refine.py
index bf603f7..85d0f20 100644
--- a/google/test/test_refine.py
+++ b/google/test/test_refine.py
@@ -190,10 +190,10 @@ class TutorialTestFacets(RefineTestCase):
         self.assertEqual(cd.numeric_count, 548)
 
 
-class TutorialTestTransformAndClustering(RefineTestCase):
+class TutorialTestEditing(RefineTestCase):
     project_file = 'louisiana-elected-officials.csv'
 
-    def test_transform(self):
+    def test_editing(self):
         # Section "3. Cell Editing": {1}
         self.project.engine.remove_all()    # redundant due to setUp
         # {2}
@@ -206,15 +206,34 @@ class TutorialTestTransformAndClustering(RefineTestCase):
         self.project.engine.add_facet(office_title_facet)
         response = self.project.compute_facets()
         self.assertEqual(len(response.facets[0].choices), 76)
-        response = self.project.text_transform(column='Office Title',
-            expression='value.trim()')
+        response = self.project.text_transform('Office Title', 'value.trim()')
         self.assertTrue('6895' in response['historyEntry']['description'])
         response = self.project.compute_facets()
         self.assertEqual(len(response.facets[0].choices), 67)
         # {5}
-        response = self.project.edit(column='Office Title',
+        response = self.project.edit('Office Title',
             'Councilmen', 'Councilman')
         self.assertTrue('13' in response['historyEntry']['description'])
+        response = self.project.compute_facets()
+        self.assertEqual(len(response.facets[0].choices), 66)
+        # {6}
+        response = self.project.compute_clusters('Office Title')
+        self.assertTrue(not response)
+        # {7}
+        clusters = self.project.compute_clusters('Office Title', 'knn')
+        self.assertEqual(len(clusters), 7)
+        self.assertEqual(len(clusters[0]), 2)
+        self.assertEqual(clusters[0][0]['value'], 'RSCC Member')
+        self.assertEqual(clusters[0][0]['count'], 233)
+        # Not strictly necessary to repeat 'Council Member' but a test
+        # of mass_edit, and it's also what the front end sends.
+        response = self.project.mass_edit('Office Title', [{
+            'from': ['Council Member', 'Councilmember'],
+            'to': 'Council Member'
+        }])
+        self.assertTrue('372' in response['historyEntry']['description'])
+        response = self.project.compute_facets()
+        self.assertEqual(len(response.facets[0].choices), 65)
 
 
 if __name__ == '__main__':