'Send standard size expressions to ``parse_num`` in
many sizes, we expect to get correct size results.
:param expr str: A string representing the size expression
:param size int: A string representing the volume size'

@given(expr=sampled_from(['KB', 'MB', 'GB', 'TB', '']), size=integers(min_value=1, max_value=100))
def test_parsenum_all_sizes(self, expr, size):

    if (expr is 'KB'):
        expected_size = int(KiB(size).to_Byte())
    elif (expr is 'MB'):
        expected_size = int(MiB(size).to_Byte())
    elif (expr is 'GB'):
        expected_size = int(GiB(size).to_Byte())
    elif (expr is 'TB'):
        expected_size = int(TiB(size).to_Byte())
    else:
        expected_size = int(Byte(size).to_Byte())
    return self.assertEqual(expected_size, int(parse_num((str(size) + expr)).to_Byte()))
