TDD'ing a Riddle

princes.rb

require "minitest/autorun"

def yes
  true
end

def no
  false
end

class Prince
  attr_reader :tell_the_truth

  def initialize(tell_the_truth:)
    @tell_the_truth = Array(tell_the_truth)
  end

  def handle_a_yes_no_statement(yes_or_no)
    handler = tell_the_truth.sample
    yes_or_no ? handler : !handler
  end

  def deterministic?
    tell_the_truth.count == 1
  end
end

def ask(askee, about:)
  askee
end

class MarriageTest < MiniTest::Test
  def test_all_the_questions
    youngest = Prince.new(tell_the_truth: no)
    middle = Prince.new(tell_the_truth: [yes, no])
    oldest = Prince.new(tell_the_truth: [yes])
    assert_predicate ask(youngest, about: [middle, oldest]), :deterministic?
    assert_predicate ask(youngest, about: [oldest, middle]), :deterministic?
    assert_predicate ask(middle, about: [youngest, oldest]), :deterministic?
    assert_predicate ask(middle, about: [oldest, youngest]), :deterministic?
    assert_predicate ask(oldest, about: [youngest, middle]), :deterministic?
    assert_predicate ask(oldest, about: [middle, youngest]), :deterministic?
  end
end