[ruby/rdoc] Rwrite test-case for rubygems_hook without Gem::TestCase

https://github.com/ruby/rdoc/commit/f8d1087ce5

test/rdoc/test_rdoc_rubygems_hook.rb

@@ -1,30 +1,30 @@
 # frozen_string_literal: true
-require 'rubygems/test_case'
+require "rubygems"
+require "fileutils"
+require "tmpdir"
 require 'rdoc/rubygems_hook'
+require "test/unit"
 
-class TestRDocRubygemsHook < Gem::TestCase
-  unless method_defined?(:assert_path_exist)
-    alias assert_path_exist assert_path_exists
-  end
-  unless method_defined?(:assert_path_not_exist)
-    alias assert_path_not_exist refute_path_exists
-  end
-  unless method_defined?(:assert_raise)
-    alias assert_raise assert_raises
-  end
-
+class TestRDocRubygemsHook < Test::Unit::TestCase
   def setup
-    super
+    FileUtils.mkdir_p File.expand_path("tmp")
 
-    @a = util_spec 'a', 2 do |s|
+    @a = Gem::Specification.new do |s|
+      s.platform    = Gem::Platform::RUBY
+      s.name        = "a"
+      s.version     = 2
       s.rdoc_options = %w[--main MyTitle]
       s.extra_rdoc_files = %w[README]
     end
+    @tempdir = Dir.mktmpdir("test_rubygems_", File.expand_path("tmp"))
 
-    write_file File.join(@tempdir, 'lib', 'a.rb')
-    write_file File.join(@tempdir, 'README')
+    @a.instance_variable_set(:@doc_dir, File.join(@tempdir, "doc"))
+    @a.instance_variable_set(:@gem_dir, File.join(@tempdir, "a-2"))
+    @a.instance_variable_set(:@full_gem_path, File.join(@tempdir, "a-2"))
 
-    install_gem @a
+    FileUtils.mkdir_p File.join(@tempdir, 'a-2', 'lib')
+    FileUtils.touch   File.join(@tempdir, 'a-2', 'lib', 'a.rb')
+    FileUtils.touch   File.join(@tempdir, 'a-2', 'README')
 
     @hook = RDoc::RubygemsHook.new @a
 
@@ -33,8 +33,10 @@ class TestRDocRubygemsHook < Gem::TestCase
     rescue Gem::DocumentError => e
       skip e.message
     end
+  end
 
-    Gem.configuration[:rdoc] = nil
+  def teardown
+    FileUtils.rm_rf File.expand_path("tmp")
   end
 
   def test_initialize