Add unit test for cell_value method on PartialRowData

bigtable/google/cloud/bigtable/row_data.py

@@ -171,7 +171,7 @@ def row_key(self):
         """
         return self._row_key
 
-    def cell_value(self, column_family_id, column_id, index=0):
+    def cell_value(self, column_family_id, column, index=0):
         """Get a cell value
 
         :type column_family_id: str
@@ -187,7 +187,7 @@ def cell_value(self, column_family_id, column_id, index=0):
         :rtype:  bytes or :class:`int`
         :returns: the cell value
         """
-        return self._cells[column_family_id][column_id][index].value
+        return self._cells[column_family_id][column][index].value
 
 
 class InvalidReadRowsResponse(RuntimeError):

bigtable/tests/unit/test_row_data.py

@@ -174,6 +174,27 @@ def test_to_dict(self):
         }
         self.assertEqual(result, expected_result)
 
+    def test_cell_value(self):
+        from google.cloud.bigtable.row_data import Cell
+
+        family_name = u'name1'
+        qual = b'col1'
+
+        timestamp = object()
+        value = b'value-bytes'
+        cell = Cell(value, timestamp)
+
+        partial_row_data = self._make_one(None)
+        partial_row_data._cells = {
+            family_name: {
+                qual: [cell]
+            }
+        }
+
+        result = partial_row_data.cell_value(family_name, qual)
+        expected_result = value
+        self.assertEqual(result, expected_result)
+
     def test_cells_property(self):
         partial_row_data = self._make_one(None)
         cells = {1: 2}