More doctests; test "find_mount_point" (using MiniMock)

Add doctests for the find_mount_point() utility method
and make it more robust while finding shortcomings of
the current implementation by unexpected behaviour that
has been checked with the doctest and mock objects.

Note the unittest requirements (minimock + coverage) in
the README file and rm the ".coverage" file on "make clean".

Makefile

@@ -135,7 +135,7 @@ $(ROSETTA_ARCHIVE):
 
 clean:
 	python setup.py clean
-	rm -f src/gpodder/*.pyc src/gpodder/*.pyo src/gpodder/*.bak MANIFEST PKG-INFO data/gpodder.gladep{,.bak} data/gpodder.glade.bak $(GLADEGETTEXT) data/messages.pot~ data/gpodder-??x??.png $(ROSETTA_ARCHIVE)
+	rm -f src/gpodder/*.pyc src/gpodder/*.pyo src/gpodder/*.bak MANIFEST PKG-INFO data/gpodder.gladep{,.bak} data/gpodder.glade.bak $(GLADEGETTEXT) data/messages.pot~ data/gpodder-??x??.png $(ROSETTA_ARCHIVE) .coverage
 	rm -rf build
 	make -C data/po clean
 

README

@@ -77,6 +77,11 @@
    * intltool
    * imagemagick
 
+ Dependencies for running unittest/doctests ("make unittest"):
+
+   * python-minimock
+   * python-coverage (optional; recommended)
+
  ============
  Installation
  ============

src/gpodder/unittests.py

@@ -27,6 +27,15 @@ import unittest
 import gettext
 import sys
 
+try:
+    import minimock
+except ImportError, e:
+    print >>sys.stderr, """
+    Error: Unit tests require the "minimock" module (python-minimock).
+    Please install it before running the unit tests.
+    """
+    sys.exit(2)
+
 # Which package and which modules in the package should be tested?
 package = 'gpodder'
 modules = ['util', 'libtagupdate']

src/gpodder/util.py

@@ -1036,8 +1036,75 @@ def find_mount_point(directory):
     it. If not, remove the last part of the path and
     re-check if it's a mount point. If the directory
     resides on your root filesystem, "/" is returned.
+
+    >>> find_mount_point('/')
+    '/'
+
+    >>> find_mount_point(u'/something')
+    Traceback (most recent call last):
+      ...
+    ValueError: Convert unicode objects to str first.
+
+    >>> find_mount_point(None)
+    Traceback (most recent call last):
+      ...
+    ValueError: Directory names should be of type str.
+
+    >>> find_mount_point(42)
+    Traceback (most recent call last):
+      ...
+    ValueError: Directory names should be of type str.
+
+    >>> from minimock import mock
+    >>> mocked_mntpoints = ('/', '/home', '/media/usbdisk', '/media/cdrom')
+    >>> mock('os.path.ismount', returns_func=lambda x: x in mocked_mntpoints)
+    >>>
+    >>> # For mocking os.getcwd(), we simply use a lambda to avoid the
+    >>> # massive output of "Called os.getcwd()" lines in this doctest
+    >>> os.getcwd = lambda: '/home/thp'
+    >>>
+    >>> find_mount_point('.')
+    Called os.path.ismount('/home/thp')
+    Called os.path.ismount('/home')
+    '/home'
+    >>> find_mount_point('relativity')
+    Called os.path.ismount('/home/thp/relativity')
+    Called os.path.ismount('/home/thp')
+    Called os.path.ismount('/home')
+    '/home'
+    >>> find_mount_point('/media/usbdisk/')
+    Called os.path.ismount('/media/usbdisk')
+    '/media/usbdisk'
+    >>> find_mount_point('/home/thp/Desktop')
+    Called os.path.ismount('/home/thp/Desktop')
+    Called os.path.ismount('/home/thp')
+    Called os.path.ismount('/home')
+    '/home'
+    >>> find_mount_point('/media/usbdisk/Podcasts/With Spaces')
+    Called os.path.ismount('/media/usbdisk/Podcasts/With Spaces')
+    Called os.path.ismount('/media/usbdisk/Podcasts')
+    Called os.path.ismount('/media/usbdisk')
+    '/media/usbdisk'
+    >>> find_mount_point('/home/')
+    Called os.path.ismount('/home')
+    '/home'
+    >>> find_mount_point('/media/cdrom/../usbdisk/blubb//')
+    Called os.path.ismount('/media/usbdisk/blubb')
+    Called os.path.ismount('/media/usbdisk')
+    '/media/usbdisk'
     """
-    while os.path.split(directory)[0] != '/':
+    if isinstance(directory, unicode):
+        # We do not accept unicode strings, because they could fail when
+        # trying to be converted to some native encoding, so fail loudly
+        # and leave it up to the callee to encode into the proper encoding.
+        raise ValueError('Convert unicode objects to str first.')
+
+    if not isinstance(directory, str):
+        raise ValueError('Directory names should be of type str.')
+
+    directory = os.path.abspath(directory)
+
+    while directory != '/':
         if os.path.ismount(directory):
             return directory
         else: