'``mount`` mounts the supplied device and returns a
``MountedFileSystem`` that can be unmounted.
The files added to mountpoint are stored on the filesystem rather than
in the mountpoint directory.'

def test_success(self):

    filename = random_name(self)
    filecontent = random_name(self)
    mount_directory1 = self.make_temporary_directory()
    fs1 = mount(self.device.device, mount_directory1)
    mount_directory1.child(filename).setContent(filecontent)
    fs1.unmount()
    self.assertRaises(UnmountError, fs1.unmount)
    self.assertEqual([], mount_directory1.children())
    mount_directory2 = self.make_temporary_directory()
    fs2 = mount(self.device.device, mount_directory2)
    self.assertEqual(filecontent, mount_directory2.child(filename).getContent())
    fs2.unmount()
