Very similar to other katas about "implementing a bot who forces the opponent to pick last something". Also, input validation is more annoying than anything.

test.expect( move(True) == "2, 3, 4, 5", "move(True) does not return '2, 3, 4, 5'")

This test case makes zero sense. True is not a integer, bool is subclass of int:

https://stackoverflow.com/a/2764099

1. The test with -1 as input surprised me, as in the description, negative integers are not mentioned as 'Invalid'.
2. By the way, why the inputs 5, 10, 15, 20 are invalid? For 20, of course, computer lost, but for the others, a one-number or a random move could be done, just as in the real game.