skimage: if --readPath points at an empty dir, create an empty expectations file

tools/tests/skimage_self_test.py

 #!/usr/bin/env python
 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Self-test for skimage.
 
 import filecmp
 import os
 import subprocess
 import sys
+import tempfile
 
 class BinaryNotFoundException(Exception):
     def __str__ (self):
         return ("Could not find binary!\n"
                 "Did you forget to build the tools project?\n"
                 "Self tests failed")
 
 # Find a path to the binary to use. Iterates through a list of possible
 # locations the binary may be.
 def PickBinaryPath(base_dir):
@@ skipping 41 matching lines @@
     DieIfFilesMismatch(expected=golden_expectations, actual=expectations_path)
 
     # Tell skimage to read back the expectations file it just wrote, and
     # confirm that the images in images_dir match it.
     subprocess.check_call([skimage_binary, "--readPath", images_dir,
                            "--readExpectationsPath", expectations_path])
 
     # TODO(scroggo): Add a test that compares expectations and image files that
     # are known to NOT match, and make sure it returns an error.
 
+    # Generate an expectations file from an empty directory.
+    empty_dir = tempfile.mkdtemp()
+    expectations_path = os.path.join(file_dir, "skimage", "output-actual",
+                                     "empty-dir", "expectations.json")
+    subprocess.check_call([skimage_binary, "--readPath", empty_dir,
+                           "--createExpectationsPath", expectations_path])
+    golden_expectations = os.path.join(file_dir, "skimage", "output-expected",
+                                       "empty-dir", "expectations.json")
+    DieIfFilesMismatch(expected=golden_expectations, actual=expectations_path)
+    os.rmdir(empty_dir)
+
+    # Generate an expectations file from a nonexistent directory.
+    expectations_path = os.path.join(file_dir, "skimage", "output-actual",
+                                     "nonexistent-dir", "expectations.json")
+    subprocess.check_call([skimage_binary, "--readPath", "/nonexistent/dir",
+                           "--createExpectationsPath", expectations_path])
+    golden_expectations = os.path.join(file_dir, "skimage", "output-expected",
+                                       "nonexistent-dir", "expectations.json")
+    DieIfFilesMismatch(expected=golden_expectations, actual=expectations_path)
+
     # Done with all tests.
     print "Self tests succeeded!"
 
 if __name__ == "__main__":
     main()