That's because it's not square root, but cubic root of 1*2*6 (as those are three numbers).

50 of them, but the numbers itself does not say much.

Apparently it does not run fast enough if you take 1.7 seconds (where?) to pass just one test.

Do you mean something like this:

test.it("should pass some random tests")
import random
for _ in range(40):
    # compute some random input
    m, n = (random.randrange(2, 11) for _ in range(2))
    matrix = [[random.randrange(-100, 101) for _ in range(n)] for _ in range(m)]
    times = random.randrange(0, 13)

    # compute the expected result
    expected = # I'm not going to spoil this kata

    # compute a string representation of the matrix
    # now before the user might change it
    matrix_str = repr(matrix)

    # do the actual testing
    actual = rotate_against_clockwise(matrix, times)
    test.assert_equals(actual, expected,
        "rotate_against_clockwise({}, {})".format(matrix_str, times))