Add assert to make sure the files argument type is valid.

tests/presubmit_unittest.py

 #!/usr/bin/env python
 # Copyright (c) 2011 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.
 
 """Unit tests for presubmit_support.py and presubmit_canned_checks.py."""
 
 # pylint is too confused.
 # pylint: disable=E1101,E1103,R0201,W0212,W0403
 
@@ skipping 333 matching lines @@
     self.assertEquals(rhs_lines[8][2], 'this is line number 23.1')
 
     self.assertEquals(rhs_lines[12][0].LocalPath(), files[3][1])
     self.assertEquals(rhs_lines[12][1], 46)
     self.assertEquals(rhs_lines[12][2], '')
 
     self.assertEquals(rhs_lines[13][0].LocalPath(), files[3][1])
     self.assertEquals(rhs_lines[13][1], 49)
     self.assertEquals(rhs_lines[13][2], 'this is line number 48.1')
 
+  def testInvalidChange(self):
+    try:
+      presubmit.SvnChange(
+          'mychange',
+          'description',
+          self.fake_root_dir,
+          ['foo/blat.cc', 'bar'],
+          0,
+          0,
+          None)
+      self.fail()
+    except AssertionError:
+      pass
+
   def testExecPresubmitScript(self):
     description_lines = ('Hello there',
                          'this is a change',
                          'STORY=http://tracker/123')
     files = [
       ['A', 'foo\\blat.cc'],
     ]
     fake_presubmit = presubmit.os.path.join(self.fake_root_dir, 'PRESUBMIT.py')
     self.mox.ReplayAll()
 
@@ skipping 399 matching lines @@
                                               self.fake_root_dir, None, None,
                                               False, output))
 
   def testMainUnversioned(self):
     # OptParser calls presubmit.os.path.exists and is a pain when mocked.
     self.UnMock(presubmit.os.path, 'exists')
     self.mox.StubOutWithMock(presubmit, 'DoPresubmitChecks')
     self.mox.StubOutWithMock(presubmit, 'ParseFiles')
     presubmit.scm.determine_scm(self.fake_root_dir).AndReturn(None)
     presubmit.ParseFiles(['random_file.txt'], None
-        ).AndReturn(['random_file.txt'])
+        ).AndReturn([('M', 'random_file.txt')])
     output = self.mox.CreateMock(presubmit.PresubmitOutput)
     output.should_continue().AndReturn(False)
 
     presubmit.DoPresubmitChecks(mox.IgnoreArg(), False, False,
                                 mox.IgnoreArg(),
                                 mox.IgnoreArg(),
                                 None, False, None).AndReturn(output)
     self.mox.ReplayAll()
 
     self.assertEquals(
@@ skipping 1470 matching lines @@
         owners_check=True)
     self.assertEqual(1, len(results))
     self.assertEqual(
         'Found line ending with white spaces in:', results[0]._message)
     self.checkstdout('')
 
 
 if __name__ == '__main__':
   import unittest
   unittest.main()