add tests for owners database module in depot_tools

tests/filesystem_mock.py

+#!/usr/bin/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.
+
+import errno
+import os
+import re
+import StringIO
+import unittest
+
+
+class MockFileSystem(object):

[M-A Ruel, 2011/03/03 16:20:46]

Personally, I think it's waaay simpler (and safer) to just create a temporary
directory on the fly and mocking it.

os.makedirs(os.path.join(base_path, 'test', 'a'))
open(os.path.join(base_path, 'test', 'OWNERS'), 'w').write('*')
open(os.path.join(base_path, 'test', 'a', 'OWNERS'), 'w').write('foo')

If you need a SCM, FakeRepos already does that. It could be interesting to have
FakeRepos to have a mode where it doesn't starts neither svnserve nor create a
git repository. 

But I don't really mind, especially that your code doesn't *write* to the file
system. Feel free to keep this design if you prefer.

+  """Stripped-down version of WebKit's webkitpy.common.system.filesystem_mock
+
+  Implements a filesystem-like interface on top of a dict of filenames ->
+  file contents. A file content value of None indicates that the file should
+  not exist (IOError will be raised if it is opened;
+  reading from a missing key raises a KeyError, not an IOError."""
+
+  def __init__(self, files=None):
+    self.files = files or {}
+    self.written_files = {}
+    self._sep = '/'
+
+  def _get_sep(self):
+    return self._sep
+
+  sep = property(_get_sep, doc='pathname separator')
+
+  def _raise_not_found(self, path):  # pylint: disable=R0201
+    raise IOError(errno.ENOENT, path, os.strerror(errno.ENOENT))
+
+  def _split(self, path):
+    return path.rsplit(self.sep, 1)
+
+  def dirname(self, path):
+    if not self.sep in path:
+      return ''
+    return self._split(path)[0]
+
+  def exists(self, path):
+    return self.isfile(path) or self.isdir(path)
+
+  def isfile(self, path):
+    return path in self.files and self.files[path] is not None
+
+  def isdir(self, path):
+    if path in self.files:
+      return False
+    if not path.endswith(self.sep):
+      path += self.sep
+
+    # We need to use a copy of the keys here in order to avoid switching
+    # to a different thread and potentially modifying the dict in
+    # mid-iteration.
+    files = self.files.keys()[:]
+    return any(f.startswith(path) for f in files)
+
+  def join(self, *comps):
+    # FIXME: might want tests for this and/or a better comment about how
+    # it works.
+    return re.sub(re.escape(os.path.sep), self.sep, os.path.join(*comps))
+
+  def open_for_reading(self, path):
+    return StringIO.StringIO(self.read_binary_file(path))
+
+  def read_binary_file(self, path):
+    # Intentionally raises KeyError if we don't recognize the path.
+    if self.files[path] is None:
+      self._raise_not_found(path)
+    return self.files[path]