Checks for exact values in core/random/bytes

[herwinw]

The spec core/random/bytes has a few checks for the exact results:

  # Should double check this is official spec
  it "returns the same numeric output for a given seed across all implementations and platforms" do
    rnd = Random.new(33)
    rnd.bytes(2).should == "\x14\\"
    rnd.bytes(1000) # skip some
    rnd.bytes(2).should == "\xA1p"
  end

The documentation of Random contains the following line:

PRNGs are currently implemented as a modified Mersenne Twister with a period of 2**19937-1.

Although it is described as being modified, I can't find any documentation on how it is modified without digging into the Ruby source code. In Natalie, we tried this using std::mt19937. This results in different output and fails the test (see natalie-lang/natalie#919)

Given that there already is a comment about whether this is the official spec, and there is no official documentation on how the MRI implementation actually works except for the code itself, I'm not sure this check should be in the spec.

[eregon]

It is intentional to test the exact values for Random, e.g. also see

spec/core/random/rand_spec.rb

Lines 208 to 211 in 1c0ea5c

	it "returns a float within a given float range" do
	Random.new(42).rand(0.0...100.0).should == 37.454011884736246
	Random.new(42).rand(-100.0...0.0).should == -62.545988115263754
	end

Because it is very valuable when running some Ruby app on another Ruby to actually have the same Random values when given the same seed (e.g. via srand).
I'll just remove that comment.