[ruby/irb] Add MultiIRB commands test

(https://github.com/ruby/irb/pull/929)

https://github.com/ruby/irb/commit/c6bbc424c3

test/irb/command/test_multi_irb_commands.rb

@@ -0,0 +1,50 @@
+require "tempfile"
+require_relative "../helper"
+
+module TestIRB
+  class MultiIRBTest < IntegrationTestCase
+    def setup
+      super
+
+      write_ruby <<~'RUBY'
+        binding.irb
+      RUBY
+    end
+
+    def test_jobs_command_with_print_deprecated_warning
+      out = run_ruby_file do
+        type "jobs"
+        type "exit"
+      end
+
+      assert_match(/Multi-irb commands are deprecated and will be removed in IRB 2\.0\.0\. Please use workspace commands instead\./, out)
+      assert_match(%r|If you have any use case for multi-irb, please leave a comment at https://github.com/ruby/irb/issues/653|, out)
+      assert_match(/#0->irb on main \(#<Thread:0x.+ run>: running\)/, out)
+    end
+
+    def test_irb_jobs_and_kill_commands
+      out = run_ruby_file do
+        type "irb"
+        type "jobs"
+        type "kill 1"
+        type "exit"
+      end
+
+      assert_match(/#0->irb on main \(#<Thread:0x.+ sleep_forever>: stop\)/, out)
+      assert_match(/#1->irb#1 on main \(#<Thread:0x.+ run>: running\)/, out)
+    end
+
+    def test_irb_fg_jobs_and_kill_commands
+      out = run_ruby_file do
+        type "irb"
+        type "fg 0"
+        type "jobs"
+        type "kill 1"
+        type "exit"
+      end
+
+      assert_match(/#0->irb on main \(#<Thread:0x.+ run>: running\)/, out)
+      assert_match(/#1->irb#1 on main \(#<Thread:0x.+ sleep_forever>: stop\)/, out)
+    end
+  end
+end