make render_pictures properly handle empty expectations file

tools/tests/render_pictures_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 the render_pictures binary.
 """
@@ skipping 251 matching lines @@
             },
             "green.skp": {
                 "whole-image": GREEN_WHOLEIMAGE,
             }
         }
     }
     self._assert_json_contents(output_json_path, expected_summary_dict)
     self._assert_directory_contents(
         write_path_dir, ['red_skp.png', 'green_skp.png'])
 
+  def test_untiled_empty_expectations_file(self):

[scroggo, 2014/05/19 13:28:32]

It looks like this function could share code with the one above. (The only
difference is the creation of the expectations file, correct?)

[epoger, 2014/05/19 14:52:00]

Good idea.  I took a stab at this; please let me know what you think.

[scroggo, 2014/05/19 15:07:38]

Looks good.

+    """Same as test_untiled, but with an empty expectations file."""
+    output_json_path = os.path.join(self._output_dir, 'actuals.json')
+    write_path_dir = self.create_empty_dir(
+        path=os.path.join(self._output_dir, 'writePath'))
+    self._generate_skps()
+    expectations_path = os.path.join(self._expectations_dir, 'empty')
+    with open(expectations_path, 'w') as fh:
+      pass
+    self._run_render_pictures([
+        '-r', self._input_skp_dir,
+        '--readJsonSummaryPath', expectations_path,
+        '--writePath', write_path_dir,
+        '--writeJsonSummaryPath', output_json_path])
+    expected_summary_dict = {
+        "header" : EXPECTED_HEADER_CONTENTS,
+        "actual-results" : {
+            "red.skp": {
+                "whole-image": modified_dict(
+                    RED_WHOLEIMAGE, {"comparisonResult" : "no-comparison"}),
+            },
+            "green.skp": {
+                "whole-image": modified_dict(
+                    GREEN_WHOLEIMAGE, {"comparisonResult" : "no-comparison"}),
+            }
+        }
+    }
+    self._assert_json_contents(output_json_path, expected_summary_dict)
+    self._assert_directory_contents(
+        write_path_dir, ['red_skp.png', 'green_skp.png'])
+
   def test_untiled_writeChecksumBasedFilenames(self):
     """Same as test_untiled, but with --writeChecksumBasedFilenames."""
     output_json_path = os.path.join(self._output_dir, 'actuals.json')
     write_path_dir = self.create_empty_dir(
         path=os.path.join(self._output_dir, 'writePath'))
     self._generate_skps()
     self._run_render_pictures(['-r', self._input_skp_dir,
                                '--writeChecksumBasedFilenames',
                                '--writePath', write_path_dir,
                                '--writeJsonSummaryPath', output_json_path])
@@ skipping 359 matching lines @@
     self.assertMultiLineEqual(prettyprinted_expected_dict,
                               prettyprinted_json_dict)
 
 
 def main():
   base_unittest.main(RenderPicturesTest)
 
 
 if __name__ == '__main__':
   main()