This patch just extends test coverage on the random library by a few lines.

I don't mind adding a test but would like it to written somewhat differently.  I'll work something up when I get a chance.  Marking this as a low priority because the code is already working fine and this is just a nice addition to improve coverage.

Sounds fine! I look forward to seeing how to do this properly!

The test code now includes this:

    def test_shuffle_random_argument(self):
        # Test random argument to shuffle.
        shuffle = self.gen.shuffle
        mock_random = unittest.mock.Mock(return_value=0.5)
        seq = bytearray(b'abcdefghijk')
        shuffle(seq, mock_random)
        mock_random.assert_called_with()

Thank you for the suggestion.