'_get_available_capacity should calculate correct value.'

def test_get_available_capacity_with_df(self):

    drv = self._driver
    df_total_size = 2620544
    df_avail = 1490560
    df_head = 'Filesystem    1K-blocks    Used    Available    Use%    Mounted    on\n'
    df_data = ('quobyte@%s    %d    996864    %d    41%%    %s' % (self.TEST_QUOBYTE_VOLUME, df_total_size, df_avail, self.TEST_MNT_POINT))
    df_output = (df_head + df_data)
    drv._get_mount_point_for_share = mock.Mock(return_value=self.TEST_MNT_POINT)
    drv._execute = mock.Mock(return_value=(df_output, None))
    self.assertEqual((df_avail, df_total_size), drv._get_available_capacity(self.TEST_QUOBYTE_VOLUME))
    drv._get_mount_point_for_share.assert_called_once_with(self.TEST_QUOBYTE_VOLUME)
    drv._execute.assert_called_once_with('df', '--portability', '--block-size', '1', self.TEST_MNT_POINT, run_as_root=self._driver._execute_as_root)
