def test_1d(tiebreaker):
# Standard Tennessee example
# https://en.wikipedia.org/wiki/Template:Tenn_voting_example
Memphis, Nashville, Chattanooga, Knoxville = 0, 1, 2, 3
election = [
*42 * [Memphis], *26 * [Nashville], *15 * [Chattanooga],
*17 * [Knoxville]
]
assert fptp(election, tiebreaker) == Memphis
# Example from Ques 9
# http://www.yorku.ca/bucovets/4380/exercises/exercises_1_a.pdf
v, w, x, y, z = 0, 1, 2, 3, 4
election = [*11 * [v], *12 * [w], *13 * [x], *14 * [y], *15 * [z]]
assert fptp(election, tiebreaker) == z
# 50% plurality but not strictly majority
election = np.array([2, 0, 2, 1])
assert fptp(election, tiebreaker) == 2
# 40% plurality, 30% for others
election = np.array([2, 0, 2, 1, 0, 2, 1, 2, 1, 0])
assert fptp(election, tiebreaker) == 2
# Example from
# http://jlmartin.faculty.ku.edu/~jlmartin/courses/math105-F11/Lectures/chapter1-part2.pdf
A, B = 0, 1
election = [*60 * [A], *40 * [B]]
assert fptp(election, tiebreaker) == A
def test_ties():
# Two-way tie between candidates 1 and 2
election = np.array([
[0, 1, 2],
[2, 0, 1],
[0, 1, 2],
[1, 2, 0],
[1, 2, 0],
[2, 0, 1],
[2, 0, 1],
[1, 2, 0],
])
# No tiebreaker:
assert fptp(election, tiebreaker=None) is None
# Mode 'order' should always prefer lowest candidate ID
assert fptp(election, tiebreaker='order') == 1
# Mode 'random' should choose all tied candidates at random
assert collect_random_results(fptp, election) == {1, 2}
# Three-way tie between 0, 1, and 2
election = np.array([
[0, 1, 2],
[0, 1, 2],
[0, 1, 2],
[1, 2, 0],
[1, 2, 0],
[1, 2, 0],
[2, 0, 1],
[2, 0, 1],
[2, 0, 1],
])
# No tiebreaker:
assert fptp(election, tiebreaker=None) is None
# Mode 'order' should always prefer lowest candidate ID
assert fptp(election, tiebreaker='order') == 0
# Mode 'random' should choose all tied candidates at random
assert collect_random_results(fptp, election) == {0, 1, 2}
def test_basic(tiebreaker):
# Standard Tennessee example
# https://en.wikipedia.org/wiki/Template:Tenn_voting_example
Memphis, Nashville, Chattanooga, Knoxville = 0, 1, 2, 3
election = [
*42 * [[Memphis, Nashville, Chattanooga, Knoxville]],
*26 * [[Nashville, Chattanooga, Knoxville, Memphis]],
*15 * [[Chattanooga, Knoxville, Nashville, Memphis]],
*17 * [[Knoxville, Chattanooga, Nashville, Memphis]],
]
assert fptp(election, tiebreaker) == Memphis
# Example from Ques 9
# http://www.yorku.ca/bucovets/4380/exercises/exercises_1_a.pdf
v, w, x, y, z = 0, 1, 2, 3, 4
election = [
*11 * [[v, w, x, y, z]],
*12 * [[w, x, y, z, v]],
*13 * [[x, v, w, y, z]],
*14 * [[y, w, v, z, x]],
*15 * [[z, v, x, w, y]],
]
assert fptp(election, tiebreaker) == z
# 50% plurality but not strictly majority
election = np.array([[2, 3, 1, 0], [0, 1, 2, 3], [2, 1, 3, 0],
[1, 0, 3, 2]])
assert fptp(election, tiebreaker) == 2
# 40% plurality, 30% for others
election = np.array([[2, 0, 1], [0, 1, 2], [2, 0, 1], [1, 2, 0], [0, 1, 2],
[2, 0, 1], [1, 0, 2], [2, 0, 1], [1, 0, 2], [0, 2,
1]])
assert fptp(election, tiebreaker) == 2
# Example from
# http://jlmartin.faculty.ku.edu/~jlmartin/courses/math105-F11/Lectures/chapter1-part2.pdf
A, B, C, D = 0, 1, 2, 3
election = [
*60 * [[A, B, C, D]],
*40 * [[B, D, C, A]],
]
assert fptp(election, tiebreaker) == A
# Example from
# https://medium.com/@t2ee6ydscv/how-ranked-choice-voting-elects-extremists-fa101b7ffb8e
r, b, g, o, y = 0, 1, 2, 3, 4
election = [
*31 * [[r, b, g, o, y]],
*5 * [[b, r, g, o, y]],
*8 * [[b, g, r, o, y]],
*1 * [[b, g, o, r, y]],
*6 * [[g, b, o, r, y]],
*1 * [[g, b, o, y, r]],
*6 * [[g, o, b, y, r]],
*2 * [[o, g, b, y, r]],
*5 * [[o, g, y, b, r]],
*7 * [[o, y, g, b, r]],
*28 * [[y, o, g, b, r]],
]
assert fptp(election) == r
def test_legit_winner_none(election):
election = np.asarray(election)
n_cands = election.shape[1]
winner = fptp(election)
assert isinstance(winner, (int, type(None)))
assert winner in set(range(n_cands)) | {None}
def test_legit_winner(election, tiebreaker):
election = np.asarray(election)
n_cands = election.shape[1]
winner = fptp(election, tiebreaker)
assert isinstance(winner, int)
assert winner in range(n_cands)
def test_invalid():
with pytest.raises(ValueError):
fptp(np.array([[[0, 1]]]))