mruby-mruby/mrbgems/mruby-random/test/random.rb

##
# Random Test

assert("Random.new") do
  r1 = Random.new(123)
  r2 = Random.new(123)
  r3 = Random.new(124)
  assert_equal(r1.rand, r2.rand)
  assert_not_equal(r1.rand, r3.rand)
end

assert("Kernel#srand") do
  srand(234)
  r1 = rand
  srand(234)
  r2 = rand
  srand(235)
  r3 = rand
  assert_equal(r1, r2)
  assert_not_equal(r1, r3)
end

assert("Random.srand") do
  Random.srand(345)
  r1 = rand
  srand(345)
  r2 = Random.rand
  Random.srand(346)
  r3 = rand
  assert_equal(r1, r2)
  assert_not_equal(r1, r3)
end

assert("Random#bytes") do
  r = Random.new(10)
  num = 11
  a = r.bytes(num)
  assert_kind_of String, a
  assert_equal num, a.bytesize
  b = r.bytes(num)
  assert_kind_of String, b
  assert_equal num, b.bytesize
  assert_not_equal a, b
  b = r.bytes(num / 2)
  assert_equal num / 2, b.bytesize
end

assert("return class of Kernel#rand") do
  assert_kind_of(Integer, rand(3))
  assert_kind_of(Integer, rand(1.5))
  skip unless Object.const_defined?(:Float)
  assert_kind_of(Float, rand)
  assert_kind_of(Float, rand(0.5))
end

assert("Array#shuffle") do
  orig = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  ary = orig.dup
  shuffled = ary.shuffle
  assert_equal(orig, ary)
  assert_not_equal(ary, shuffled)
  assert_equal(orig, shuffled.sort)
end

assert('Array#shuffle!') do
  orig = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  ary = orig.dup
  assert_same(ary, ary.shuffle!)
  assert_not_equal(orig, ary)
  assert_equal(orig, ary.sort)
end

assert("Array#shuffle(random)") do
  assert_raise(TypeError) do
    # this will cause an exception due to the wrong argument
    [1, 2].shuffle(random: "Not a Random instance")
  end

  # verify that the same seed causes the same results
  ary = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  shuffled1 = ary.shuffle(random: Random.new(345))
  shuffled2 = ary.shuffle(random: Random.new(345))
  shuffled3 = ary.shuffle(random: Random.new(346))
  assert_equal(shuffled1, shuffled2)
  assert_not_equal(shuffled1, shuffled3)
end

assert('Array#shuffle!(random)') do
  assert_raise(TypeError) do
    # this will cause an exception due to the wrong argument
    [1, 2].shuffle!(random: "Not a Random instance")
  end

  # verify that the same seed causes the same results
  ary1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  ary1.shuffle!(random: Random.new(345))
  ary2 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  ary2.shuffle!(random: Random.new(345))
  ary3 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  ary3.shuffle!(random: Random.new(346))
  assert_equal(ary1, ary2)
  assert_not_equal(ary1, ary3)
end

assert('Array#sample') do
  100.times do
    assert_include([0, 1, 2], [2, 1, 0].sample)
    [2, 1, 0].sample(2).each { |sample| assert_include([0, 1, 2], sample) }
    h = {}
    (1..10).to_a.sample(7).each do |sample|
      assert_not_include(h, sample)
      h[sample] = true
    end
  end

  assert_nil([].sample)
  assert_equal([], [].sample(1))
  assert_equal([], [2, 1].sample(0))
  assert_raise(TypeError) { [2, 1].sample(true) }
  assert_raise(ArgumentError) { [2, 1].sample(-1) }
end

assert('Array#sample(random)') do
  assert_raise(TypeError) do
    # this will cause an exception due to the wrong argument
    [1, 2].sample(2, random: "Not a Random instance")
  end

  # verify that the same seed causes the same results
  ary = (1..10).to_a
  srand(15)
  samples1 = ary.sample(4)
  samples2 = ary.sample(4, random: Random.new(15))
  samples3 = ary.sample(4, random: Random.new(16))
  assert_equal(samples1, samples2)
  assert_not_equal(samples1, samples3)
end

assert("Kernel#rand()") do
  100.times {
    assert_include(0.0..1.0, rand)
    assert_include(0...100, rand(0...100))
    assert_include(0...100, rand(100))
  }

  assert_equal(rand(0...0), nil)
  assert_equal(rand(0.0...0), nil)
  assert_equal(rand(0...0.0), nil)
  assert_equal(rand(0.0...0.0), nil)
  assert_equal(rand(1..0), nil)
end

assert("Kernel#rand integer range overflow") do
  # Width-independent guard behaviour for reversed/empty/single ranges.
  assert_equal(5, rand(5..5))   # single-element inclusive range
  assert_nil(rand(5...5))       # empty exclusive range
  assert_nil(rand(10..3))       # reversed inclusive range
  assert_nil(rand(10...3))      # reversed exclusive range
  100.times { assert_include(3..7, rand(3..7)) }

  # Wide fixnum ranges whose span exceeds the mrb_int range only exist on
  # 64-bit mrb_int builds. Such bounds used to overflow `end - begin` in C
  # (UndefinedBehaviorSanitizer signed-integer-overflow), found via a
  # minimized mruby_fuzzer testcase. On 32-bit mrb_int (or when bigint
  # promotes the bounds) these take a different path, so probe the
  # integer-range path first and skip if absent.
  hi = ((1 << 62) + (1 << 61)) rescue nil
  if hi && (Integer === (rand(-hi..hi) rescue nil))
    lo = -hi
    # reversed wide range -> nil; old code overflowed `end - begin`.
    assert_nil(rand(hi..lo))
    assert_nil(rand(hi...lo))
    # valid wide range -> in-range Integer; old code overflowed and wrongly
    # returned nil instead of a uniform value.
    100.times do
      v = rand(lo..hi)
      assert_kind_of(Integer, v)
      assert_true(lo <= v && v <= hi)
    end
  end
end