teach rebaseline_server how to compare results of multiple render_pictures runs

gm/rebaseline_server/results_test.py

+#!/usr/bin/python
+
+"""
+Copyright 2014 Google Inc.
+
+Use of this source code is governed by a BSD-style license that can be
+found in the LICENSE file.
+
+Test results.py
+
+"""
+
+# Imports from within Skia
+import base_unittest
+import results
+
+
+class ResultsTest(base_unittest.TestCase):
+
+  def test_combine_subdicts_typical(self):
+    """Test combine_subdicts() with no merge conflicts. """
+    input_dict = {
+      "failed" : {
+        "changed.png" : [ "bitmap-64bitMD5", 8891695120562235492 ],
+      },
+      "no-comparison" : {
+        "unchanged.png" : [ "bitmap-64bitMD5", 11092453015575919668 ],
+      }
+    }
+    expected_output_dict = {
+      "changed.png" : [ "bitmap-64bitMD5", 8891695120562235492 ],
+      "unchanged.png" : [ "bitmap-64bitMD5", 11092453015575919668 ],
+    }
+    actual_output_dict = results.BaseComparisons.combine_subdicts(
+        input_dict=input_dict)
+    self.assertEqual(actual_output_dict, expected_output_dict)
+
+  def test_combine_subdicts_with_merge_conflict(self):
+    """Test combine_subdicts() with a merge conflict. """
+    input_dict = {
+      "failed" : {
+        "changed.png" : [ "bitmap-64bitMD5", 8891695120562235492 ],
+      },
+      "no-comparison" : {
+        "changed.png" : [ "bitmap-64bitMD5", 11092453015575919668 ],
+      }
+    }
+    with self.assertRaises(Exception):
+      actual_output_dict = results.BaseComparisons.combine_subdicts(
+          input_dict=input_dict)
+
+
+def main():
+  base_unittest.main(ResultsTest)
+
+
+if __name__ == '__main__':
+  main()