Suppress constant redefinition warnings

test/irb/test_color.rb

@@ -153,13 +153,15 @@ module TestIRB
       end
     end
 
+    IRBTestColorPrinter = Struct.new(:a)
+
     def test_color_printer
       unless ripper_lexer_scan_supported?
         skip 'Ripper::Lexer#scan is supported in Ruby 2.7+'
       end
       {
         1 => "#{BLUE}#{BOLD}1#{CLEAR}\n",
-        Struct.new('IRBTestColorPrinter', :a).new('test') => "#{GREEN}#<struct Struct::IRBTestColorPrinter#{CLEAR} a#{GREEN}=#{CLEAR}#{RED}#{BOLD}\"#{CLEAR}#{RED}test#{CLEAR}#{RED}#{BOLD}\"#{CLEAR}#{GREEN}>#{CLEAR}\n",
+        IRBTestColorPrinter.new('test') => "#{GREEN}#<struct TestIRB::TestColor::IRBTestColorPrinter#{CLEAR} a#{GREEN}=#{CLEAR}#{RED}#{BOLD}\"#{CLEAR}#{RED}test#{CLEAR}#{RED}#{BOLD}\"#{CLEAR}#{GREEN}>#{CLEAR}\n",
         Ripper::Lexer.new('1').scan => "[#{GREEN}#<Ripper::Lexer::Elem:#{CLEAR} on_int@1:0 END token: #{RED}#{BOLD}\"#{CLEAR}#{RED}1#{CLEAR}#{RED}#{BOLD}\"#{CLEAR}#{GREEN}>#{CLEAR}]\n",
       }.each do |object, result|
         actual = with_term { IRB::ColorPrinter.pp(object, '') }

test/ruby/test_marshal.rb

@@ -58,6 +58,8 @@ class TestMarshal < Test::Unit::TestCase
     TestMarshal.instance_eval { remove_const :StructOrNot }
     TestMarshal.const_set :StructOrNot, Class.new
     assert_raise(TypeError, "[ruby-dev:31709]") { Marshal.load(s) }
+  ensure
+    TestMarshal.instance_eval { remove_const :StructOrNot }
   end
 
   def test_struct_invalid_members
@@ -66,6 +68,8 @@ class TestMarshal < Test::Unit::TestCase
       Marshal.load("\004\bIc&TestMarshal::StructInvalidMembers\006:\020__members__\"\bfoo")
       TestMarshal::StructInvalidMembers.members
     }
+  ensure
+    TestMarshal.instance_eval { remove_const :StructInvalidMembers }
   end
 
   class C

test/ruby/test_module.rb

@@ -793,6 +793,8 @@ class TestModule < Test::Unit::TestCase
     assert_equal(prefix+"C", m.const_get(:C).name)
     c = m.class_eval("Bug15891 = Class.new.freeze")
     assert_equal(prefix+"Bug15891", c.name)
+  ensure
+    self.class.class_eval {remove_const(:M)}
   end
 
   def test_private_class_method