Renamed Minitest::SEED to Minitest.seed

+ Calling `srand Minitest.seed` before all shuffles to ensure determinism.

This defends against other tests/libraries calling srand themselves
and messing up minitest's seeded ordering.

[git-p4: depot-paths = "//src/minitest/dev/": change = 13428]

lib/minitest.rb

@@ -11,13 +11,6 @@ require "etc"
 module Minitest
   VERSION = "5.15.0" # :nodoc:
 
-  ##
-  # The random seed used for this run.
-  #
-  # Set via Minitest.run after processing args.
-
-  SEED = nil
-
   @@installed_at_exit ||= false
   @@after_run = []
   @extensions = []
@@ -27,9 +20,14 @@ module Minitest
   end
 
   ##
-  # :call-seq:
-  #   parallel_executor # => Parallel::Executor
+  # The random seed used for this run. This is used to srand at the
+  # start of the run and between each +Runnable.run+.
   #
+  # Set via Minitest.run after processing args.
+
+  cattr_accessor :seed
+
+  ##
   # Parallel test executor
 
   cattr_accessor :parallel_executor
@@ -144,10 +142,8 @@ module Minitest
 
     options = process_args args
 
-    unless defined?(Minitest::SEED) && Minitest::SEED then
-      remove_const :SEED
-      const_set :SEED, options[:seed]
-    end
+    Minitest.seed = options[:seed]
+    srand Minitest.seed
 
     reporter = CompositeReporter.new
     reporter << SummaryReporter.new(options[:io], options)
@@ -258,8 +254,6 @@ module Minitest
       orig_args << "--seed" << options[:seed].to_s
     end
 
-    srand options[:seed]
-
     options[:args] = orig_args.map { |s|
       s =~ /[\s|&<>$()]/ ? s.inspect : s
     }.join " "

lib/minitest/test.rb

@@ -67,6 +67,7 @@ module Minitest
 
       case self.test_order
       when :random, :parallel then
+        srand Minitest.seed
         methods.sort.shuffle
       when :alpha, :sorted then
         methods.sort

test/minitest/metametameta.rb

@@ -129,7 +129,7 @@ class MetaMetaMetaTestCase < Minitest::Test
 
   def setup
     super
-    srand 42
+    Minitest.seed = 42
     Minitest::Test.reset
     @tu = nil
   end

test/minitest/test_minitest_reporter.rb

@@ -30,6 +30,7 @@ class TestMinitestReporter < MetaMetaMetaTestCase
   end
 
   def setup
+    super
     self.io = StringIO.new("")
     self.r  = new_composite_reporter
   end

test/minitest/test_minitest_test.rb

@@ -331,7 +331,7 @@ class TestMinitestRunner < MetaMetaMetaTestCase
   end
 
   def test_seed # this is set for THIS run, so I'm not testing it's actual value
-    assert_instance_of Integer, Minitest::SEED
+    assert_instance_of Integer, Minitest.seed
   end
 
   def test_run_failing_filtered
@@ -918,7 +918,7 @@ class TestMinitestUnitTestCase < Minitest::Test
     random_tests_3 = sample_test_case 1_000
 
     assert_equal random_tests_1, random_tests_2
-    refute_equal random_tests_1, random_tests_3
+    assert_equal random_tests_1, random_tests_3
   end
 
   def test_runnable_methods_sorted