[ruby/irb] Always add input method when calling Irb.new in tests

When passes input method as nil to Context.new through Irb.new,
ReidlineInputMethod.new is executed and the global internal state of Reline is
rewritten, therefore other tests are failed in the Ruby repository. This
commit changes to use TestInputMethod.

https://github.com/ruby/irb/commit/010dce9210

test/irb/test_cmd.rb

@@ -5,6 +5,32 @@ require "irb/extend-command"
 
 module TestIRB
   class ExtendCommand < Test::Unit::TestCase
+    class TestInputMethod < ::IRB::InputMethod
+      attr_reader :list, :line_no
+
+      def initialize(list = [])
+        super("test")
+        @line_no = 0
+        @list = list
+      end
+
+      def gets
+        @list[@line_no]&.tap {@line_no += 1}
+      end
+
+      def eof?
+        @line_no >= @list.size
+      end
+
+      def encoding
+        Encoding.default_external
+      end
+
+      def reset
+        @line_no = 0
+      end
+    end
+
     def setup
       @pwd = Dir.pwd
       @tmpdir = File.join(Dir.tmpdir, "test_reline_config_#{$$}")
@@ -44,12 +70,12 @@ module TestIRB
       IRB.conf[:USE_SINGLELINE] = false
       IRB.conf[:VERBOSE] = false
       workspace = IRB::WorkSpace.new(self)
-      irb = IRB::Irb.new(workspace)
+      irb = IRB::Irb.new(workspace, TestInputMethod.new([]))
       IRB.conf[:MAIN_CONTEXT] = irb.context
       expected = %r{
         Ruby\sversion: .+\n
         IRB\sversion:\sirb .+\n
-        InputMethod:\sReidlineInputMethod\swith\sReline .+ and .+\n
+        InputMethod:\sAbstract\sInputMethod\n
         \.irbrc\spath: .+\n
         RUBY_PLATFORM: .+
       }x
@@ -64,12 +90,12 @@ module TestIRB
       IRB.conf[:USE_SINGLELINE] = true
       IRB.conf[:VERBOSE] = false
       workspace = IRB::WorkSpace.new(self)
-      irb = IRB::Irb.new(workspace)
+      irb = IRB::Irb.new(workspace, TestInputMethod.new([]))
       IRB.conf[:MAIN_CONTEXT] = irb.context
       expected = %r{
         Ruby\sversion: .+\n
         IRB\sversion:\sirb .+\n
-        InputMethod:\sReadlineInputMethod\swith .+ and .+\n
+        InputMethod:\sAbstract\sInputMethod\n
         \.irbrc\spath: .+\n
         RUBY_PLATFORM: .+
       }x
@@ -87,12 +113,12 @@ module TestIRB
       IRB.conf[:USE_SINGLELINE] = false
       IRB.conf[:VERBOSE] = false
       workspace = IRB::WorkSpace.new(self)
-      irb = IRB::Irb.new(workspace)
+      irb = IRB::Irb.new(workspace, TestInputMethod.new([]))
       IRB.conf[:MAIN_CONTEXT] = irb.context
       expected = %r{
         Ruby\sversion: .+\n
         IRB\sversion:\sirb .+\n
-        InputMethod:\sReidlineInputMethod\swith\sReline\s[^ ]+(?!\sand\s.+)\n
+        InputMethod:\sAbstract\sInputMethod\n
         RUBY_PLATFORM: .+\n
         \z
       }x
@@ -114,12 +140,12 @@ module TestIRB
       IRB.conf[:USE_SINGLELINE] = true
       IRB.conf[:VERBOSE] = false
       workspace = IRB::WorkSpace.new(self)
-      irb = IRB::Irb.new(workspace)
+      irb = IRB::Irb.new(workspace, TestInputMethod.new([]))
       IRB.conf[:MAIN_CONTEXT] = irb.context
       expected = %r{
         Ruby\sversion: .+\n
         IRB\sversion:\sirb .+\n
-        InputMethod:\sReadlineInputMethod\swith\s(?~.*\sand\s.+)\n
+        InputMethod:\sAbstract\sInputMethod\n
         RUBY_PLATFORM: .+\n
         \z
       }x
@@ -130,32 +156,6 @@ module TestIRB
       IRB.const_set(:IRBRC_EXT, ext_backup)
     end
 
-    class TestInputMethod < ::IRB::InputMethod
-      attr_reader :list, :line_no
-
-      def initialize(list = [])
-        super("test")
-        @line_no = 0
-        @list = list
-      end
-
-      def gets
-        @list[@line_no]&.tap {@line_no += 1}
-      end
-
-      def eof?
-        @line_no >= @list.size
-      end
-
-      def encoding
-        Encoding.default_external
-      end
-
-      def reset
-        @line_no = 0
-      end
-    end
-
     def test_measure
       IRB.init_config(nil)
       IRB.conf[:PROMPT] = {
@@ -376,15 +376,14 @@ module TestIRB
     end
 
     def test_ls
-      IRB.init_config(nil)
-      workspace = IRB::WorkSpace.new(self)
-      IRB.conf[:VERBOSE] = false
-      irb = IRB::Irb.new(workspace)
-      IRB.conf[:MAIN_CONTEXT] = irb.context
       input = TestInputMethod.new([
         "ls Object.new.tap { |o| o.instance_variable_set(:@a, 1) }\n",
       ])
-      irb = IRB::Irb.new(IRB::WorkSpace.new(Object.new), input)
+      IRB.init_config(nil)
+      workspace = IRB::WorkSpace.new(self)
+      irb = IRB::Irb.new(workspace, input)
+      IRB.conf[:VERBOSE] = false
+      IRB.conf[:MAIN_CONTEXT] = irb.context
       irb.context.return_format = "=> %s\n"
       out, err = capture_output do
         irb.eval_input
@@ -394,15 +393,14 @@ module TestIRB
     end
 
     def test_whereami
-      IRB.init_config(nil)
-      workspace = IRB::WorkSpace.new(self)
-      IRB.conf[:VERBOSE] = false
-      irb = IRB::Irb.new(workspace)
-      IRB.conf[:MAIN_CONTEXT] = irb.context
       input = TestInputMethod.new([
         "whereami\n",
       ])
-      irb = IRB::Irb.new(IRB::WorkSpace.new(Object.new), input)
+      IRB.init_config(nil)
+      workspace = IRB::WorkSpace.new(self)
+      irb = IRB::Irb.new(workspace, input)
+      IRB.conf[:VERBOSE] = false
+      IRB.conf[:MAIN_CONTEXT] = irb.context
       irb.context.return_format = "=> %s\n"
       out, err = capture_output do
         irb.eval_input