https://git.ruby-lang.org/ruby.git/commit/?id=8f99bfa26d

From 8f99bfa26d0bd99089f0f38af3666a89e8432265 Mon Sep 17 00:00:00 2001
From: Yusuke Endoh <mame@r...>
Date: Mon, 15 Jun 2020 13:18:56 +0900
Subject: tool/lib/minitest/unit.rb: Reproducible shuffle of test suites

... based on CRC32 of names of the test suites.

Formerly, `make test-all` randomized the order of the test suites by
using `Array#shuffle`.  It also shows `--seed N` to reproduce the order,
but it was not reproducible when a suite set is different.

This change sorts the suites by CRC32 hash of the suite names with a
salt generated by the seed.

diff --git a/tool/lib/minitest/unit.rb b/tool/lib/minitest/unit.rb
index 707dcfb..8c2a970 100644
--- a/tool/lib/minitest/unit.rb
+++ b/tool/lib/minitest/unit.rb
@@ -1407,7 +1407,18 @@ module MiniTest https://github.com/ruby/ruby/blob/trunk/tool/lib/minitest/unit.rb#L1407
         suites = @@test_suites.keys
         case self.test_order
         when :random
-          suites.shuffle
+          # shuffle test suites based on CRC32 of their names
+          salt = "\n" + rand(1 << 32).to_s
+          crc_tbl = (0..255).map do |i|
+            (0..7).inject(i) {|c,| (c & 1 == 1) ? (0xEDB88320 ^ (c >> 1)) : (c >> 1) }
+          end
+          suites = suites.sort_by do |suite|
+            crc32 = 0xffffffff
+            (suite.name + salt).bytes do |data|
+              crc32 = crc_tbl[(crc32 ^ data) & 0xff] ^ (crc32 >> 8)
+            end
+            crc32 ^ 0xffffffff
+          end
         when :nosort
           suites
         else
-- 
cgit v0.10.2


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