Fixed inconsistent require order for assertions and core_assertions

Merged: https://github.com/ruby/ruby/pull/4813

test/ruby/test_module.rb

@@ -1046,6 +1046,7 @@ class TestModule < Test::Unit::TestCase
 
   def test_attr_obsoleted_flag
     c = Class.new do
+      extend Test::Unit::Assertions
       extend Test::Unit::CoreAssertions
       def initialize
         @foo = :foo

tool/lib/core_assertions.rb

@@ -25,9 +25,7 @@ module Test
 
     module CoreAssertions
       require_relative 'envutil'
-
       require 'pp'
-      include Test::Unit::Assertions
 
       def mu_pp(obj) #:nodoc:
         obj.pretty_inspect.chomp

tool/lib/test/unit/assertions.rb

@@ -1,5 +1,4 @@
 # frozen_string_literal: true
-require_relative '../../core_assertions'
 require 'pp'
 
 module Test

tool/lib/test/unit/testcase.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 require 'test/unit/assertions'
+require_relative '../../core_assertions'
 
 module Test
   module Unit
@@ -143,6 +144,9 @@ module Test
     # See MiniTest::Assertions
 
     class TestCase
+      include Assertions
+      include CoreAssertions
+
       include LifecycleHooks
       include Guard
       extend Guard
@@ -332,8 +336,6 @@ module Test
 
       def teardown; end
 
-      include CoreAssertions
-
       def on_parallel_worker?
         false
       end

tool/test/webrick/utils.rb

@@ -36,6 +36,8 @@ module TestWEBrick
   RubyBinArray << "-I" << "#{File.dirname(EnvUtil.rubybin)}/.ext/#{RUBY_PLATFORM}"
 
   require "test/unit" unless defined?(Test::Unit)
+  include Test::Unit::Assertions
+  extend Test::Unit::Assertions
   include Test::Unit::CoreAssertions
   extend Test::Unit::CoreAssertions