Skip commits that don't generate a patch + fixes to get export working

third_party/WebKit/Tools/Scripts/webkitpy/w3c/chromium_commit_unittest.py

 # Copyright 2016 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.
 
 import unittest
 from webkitpy.common.host_mock import MockHost
 from webkitpy.common.system.executive_mock import MockExecutive2
-from webkitpy.w3c.chromium_commit import ChromiumCommit
+from webkitpy.w3c.chromium_commit import ChromiumCommit, WPT_DIR
 
 
 class ChromiumCommitTest(unittest.TestCase):
 
     def test_accepts_sha(self):
         chromium_commit = ChromiumCommit(MockHost(), sha='deadbeefcafe')
 
         self.assertEqual(chromium_commit.sha, 'deadbeefcafe')
         self.assertIsNone(chromium_commit.position)
 
     def test_derives_sha_from_position(self):
         host = MockHost()
         host.executive = MockExecutive2(output='deadbeefcafe')
         pos = 'Cr-Commit-Position: refs/heads/master@{#789}'
         chromium_commit = ChromiumCommit(host, position=pos)
 
         self.assertEqual(chromium_commit.position, 'refs/heads/master@{#789}')
         self.assertEqual(chromium_commit.sha, 'deadbeefcafe')
+
+    def test_filtered_changed_files_blacklist(self):
+        host = MockHost()
+
+        fake_files = ['file1', 'MANIFEST.json', 'file3']
+        qualified_fake_files = [WPT_DIR + f for f in fake_files]
+
+        stub_commands = {
+            'diff-tree': '\n'.join(qualified_fake_files),
+            'crrev-parse': 'fake rev',
+        }
+
+        def mock_command(args):
+            if args[1] in stub_commands:
+                return stub_commands[args[1]]
+            else:
+                raise Exception('Unexpected command called: %s' % args)
+
+        host.executive = MockExecutive2(run_command_fn=mock_command)
+        pos = 'Cr-Commit-Position: refs/heads/master@{#789}'
+        chromium_commit = ChromiumCommit(host, position=pos)
+
+        files = chromium_commit.filtered_changed_files()
+
+        expected_files = ['file1', 'file3']
+        qualified_expected_files = [WPT_DIR + f for f in expected_files]
+
+        self.assertEqual(files, qualified_expected_files)