diff --git a/tool/lib/test/unit/assertions.rb b/tool/lib/test/unit/assertions.rb
index 7e5b8d55d3..48ee458b34 100644
--- a/tool/lib/test/unit/assertions.rb
+++ b/tool/lib/test/unit/assertions.rb
@@ -48,53 +48,6 @@ module Test
         assert yield, *msgs
       end
 
-      # :call-seq:
-      #   assert_raise( *args, &block )
-      #
-      #Tests if the given block raises an exception. Acceptable exception
-      #types may be given as optional arguments. If the last argument is a
-      #String, it will be used as the error message.
-      #
-      #    assert_raise do #Fails, no Exceptions are raised
-      #    end
-      #
-      #    assert_raise NameError do
-      #      puts x  #Raises NameError, so assertion succeeds
-      #    end
-      def assert_raise(*exp, &b)
-        case exp.last
-        when String, Proc
-          msg = exp.pop
-        end
-
-        begin
-          yield
-        rescue MiniTest::Skip => e
-          return e if exp.include? MiniTest::Skip
-          raise e
-        rescue Exception => e
-          expected = exp.any? { |ex|
-            if ex.instance_of? Module then
-              e.kind_of? ex
-            else
-              e.instance_of? ex
-            end
-          }
-
-          assert expected, proc {
-            exception_details(e, message(msg) {"#{mu_pp(exp)} exception expected, not"}.call)
-          }
-
-          return e
-        ensure
-          unless e
-            exp = exp.first if exp.size == 1
-
-            flunk(message(msg) {"#{mu_pp(exp)} expected but nothing was raised"})
-          end
-        end
-      end
-
       def assert_raises(*exp, &b)
         raise NoMethodError, "use assert_raise", caller
       end
@@ -611,38 +564,6 @@ EOT
         end
       end
 
-      # threads should respond to shift method.
-      # Array can be used.
-      def assert_join_threads(threads, message = nil)
-        errs = []
-        values = []
-        while th = threads.shift
-          begin
-            values << th.value
-          rescue Exception
-            errs << [th, $!]
-            th = nil
-          end
-        end
-        values
-      ensure
-        if th&.alive?
-          th.raise(Timeout::Error.new)
-          th.join rescue errs << [th, $!]
-        end
-        if !errs.empty?
-          msg = "exceptions on #{errs.length} threads:\n" +
-            errs.map {|t, err|
-            "#{t.inspect}:\n" +
-              err.full_message(highlight: false, order: :top)
-          }.join("\n---\n")
-          if message
-            msg = "#{message}\n#{msg}"
-          end
-          raise MiniTest::Assertion, msg
-        end
-      end
-
       def assert_all_assertions_foreach(msg = nil, *keys, &block)
         all = AllFailures.new
         all.foreach(*keys, &block)
@@ -655,24 +576,6 @@ EOT
         template &&= template.chomp
         template.gsub(/\G((?:[^\\]|\\.)*?)(\\)?\?/) { $1 + ($2 ? "?" : mu_pp(arguments.shift)) }
       end
-
-      def message(msg = nil, *args, &default) # :nodoc:
-        if Proc === msg
-          super(nil, *args) do
-            ary = [msg.call, (default.call if default)].compact.reject(&:empty?)
-            if 1 < ary.length
-              ary[0...-1] = ary[0...-1].map {|str| str.sub(/(?<!\.)\z/, '.') }
-            end
-            begin
-              ary.join("\n")
-            rescue Encoding::CompatibilityError
-              ary.map(&:b).join("\n")
-            end
-          end
-        else
-          super
-        end
-      end
     end
   end
 end
diff --git a/tool/lib/test/unit/core_assertions.rb b/tool/lib/test/unit/core_assertions.rb
index 6e564c9a3f..f3cb32a7e6 100644
--- a/tool/lib/test/unit/core_assertions.rb
+++ b/tool/lib/test/unit/core_assertions.rb
@@ -2,34 +2,40 @@
 
 module Test
   module Unit
+    module Assertions
+      def _assertions= n # :nodoc:
+        @_assertions = n
+      end
+
+      def _assertions # :nodoc:
+        @_assertions ||= 0
+      end
+
+      ##
+      # Returns a proc that will output +msg+ along with the default message.
+
+      def message msg = nil, ending = nil, &default
+        proc {
+          msg = msg.call.chomp(".") if Proc === msg
+          custom_message = "#{msg}.\n" unless msg.nil? or msg.to_s.empty?
+          "#{custom_message}#{default.call}#{ending || "."}"
+        }
+      end
+    end
+
     module CoreAssertions
       if defined?(MiniTest)
         require_relative '../../envutil'
         # for ruby core testing
         include MiniTest::Assertions
       else
+        module MiniTest
+          class Skip; end
+        end
+
         require 'pp'
         require_relative 'envutil'
         include Test::Unit::Assertions
-
-        def _assertions= n # :nodoc:
-          @_assertions = n
-        end
-
-        def _assertions # :nodoc:
-          @_assertions ||= 0
-        end
-
-        ##
-        # Returns a proc that will output +msg+ along with the default message.
-
-        def message msg = nil, ending = nil, &default
-          proc {
-            msg = msg.call.chomp(".") if Proc === msg
-            custom_message = "#{msg}.\n" unless msg.nil? or msg.to_s.empty?
-            "#{custom_message}#{default.call}#{ending || "."}"
-          }
-        end
       end
 
       def mu_pp(obj) #:nodoc:
@@ -172,6 +178,53 @@ eom
         ret
       end
 
+      # :call-seq:
+      #   assert_raise( *args, &block )
+      #
+      #Tests if the given block raises an exception. Acceptable exception
+      #types may be given as optional arguments. If the last argument is a
+      #String, it will be used as the error message.
+      #
+      #    assert_raise do #Fails, no Exceptions are raised
+      #    end
+      #
+      #    assert_raise NameError do
+      #      puts x  #Raises NameError, so assertion succeeds
+      #    end
+      def assert_raise(*exp, &b)
+        case exp.last
+        when String, Proc
+          msg = exp.pop
+        end
+
+        begin
+          yield
+        rescue MiniTest::Skip => e
+          return e if exp.include? MiniTest::Skip
+          raise e
+        rescue Exception => e
+          expected = exp.any? { |ex|
+            if ex.instance_of? Module then
+              e.kind_of? ex
+            else
+              e.instance_of? ex
+            end
+          }
+
+          assert expected, proc {
+            exception_details(e, message(msg) {"#{mu_pp(exp)} exception expected, not"}.call)
+          }
+
+          return e
+        ensure
+          unless e
+            exp = exp.first if exp.size == 1
+
+            flunk(message(msg) {"#{mu_pp(exp)} expected but nothing was raised"})
+          end
+        end
+      end
+
       # :call-seq:
       #   assert_raise_with_message(exception, expected, msg = nil, &block)
       #
@@ -301,6 +354,38 @@ eom
         end
       end
 
+      # threads should respond to shift method.
+      # Array can be used.
+      def assert_join_threads(threads, message = nil)
+        errs = []
+        values = []
+        while th = threads.shift
+          begin
+            values << th.value
+          rescue Exception
+            errs << [th, $!]
+            th = nil
+          end
+        end
+        values
+      ensure
+        if th&.alive?
+          th.raise(Timeout::Error.new)
+          th.join rescue errs << [th, $!]
+        end
+        if !errs.empty?
+          msg = "exceptions on #{errs.length} threads:\n" +
+            errs.map {|t, err|
+            "#{t.inspect}:\n" +
+              err.full_message(highlight: false, order: :top)
+          }.join("\n---\n")
+          if message
+            msg = "#{message}\n#{msg}"
+          end
+          raise MiniTest::Assertion, msg
+        end
+      end
+
       def assert_all_assertions(msg = nil)
         all = AllFailures.new
         yield all
@@ -309,6 +394,23 @@ eom
       end
       alias all_assertions assert_all_assertions
 
+      def message(msg = nil, *args, &default) # :nodoc:
+        if Proc === msg
+          super(nil, *args) do
+            ary = [msg.call, (default.call if default)].compact.reject(&:empty?)
+            if 1 < ary.length
+              ary[0...-1] = ary[0...-1].map {|str| str.sub(/(?<!\.)\z/, '.') }
+            end
+            begin
+              ary.join("\n")
+            rescue Encoding::CompatibilityError
+              ary.map(&:b).join("\n")
+            end
+          end
+        else
+          super
+        end
+      end
     end
   end
 end