rank-king/test/rank_king_test.rb

require "minitest"

require "rank_king"

class TestRankKing < Minitest::Test
  def setup
    @pool = Pool.create(name: "pool")
    @axis = Axis.create(pool: @pool, name: "axis")
    @items = (?a..?d).map { Item.create(pool: @pool, title: _1) }
  end

  def test_rank_king
    ratings = @pool.items.map {|item| Rating.first(axis: @axis, item:) || OS.rating }
    original_sigma_sq = Math.sqrt(ratings.sum { _1.sigma ** 2 })

    game = RankKing.suggest_game(@axis)
    winner, loser = game.shuffle
    RankKing.rank(@axis, winner:, loser:)

    sigma_sq = Math.sqrt(@axis.ratings.sum { _1.sigma ** 2 })
    assert original_sigma_sq > sigma_sq
  end
end