[ruby/irb] Add tests for truncated show doc dialog

But pending them now because they need dummy document data to show doc.

https://github.com/ruby/irb/commit/ac471ee14e

test/irb/yamatanooroti/test_rendering.rb

@@ -170,6 +170,52 @@ begin
       EOC
     end
 
+    def test_autocomplete_with_showdoc_in_gaps_on_narrow_screen_right
+      pend "Needs a dummy document to show doc"
+      write_irbrc <<~'LINES'
+        IRB.conf[:PROMPT][:MY_PROMPT] = {
+          :PROMPT_I => "%03n> ",
+          :PROMPT_N => "%03n> ",
+          :PROMPT_S => "%03n> ",
+          :PROMPT_C => "%03n> "
+        }
+        IRB.conf[:PROMPT_MODE] = :MY_PROMPT
+        puts 'start IRB'
+      LINES
+      start_terminal(4, 19, %W{ruby -I/home/aycabta/ruby/reline/lib -I#{@pwd}/lib #{@pwd}/exe/irb}, startup_message: 'start IRB')
+      write("Str\C-i")
+      close
+      assert_screen(<<~EOC)
+        001> String
+             StringPress A
+             StructString
+                   of byte
+      EOC
+    end
+
+    def test_autocomplete_with_showdoc_in_gaps_on_narrow_screen_left
+      pend "Needs a dummy document to show doc"
+      write_irbrc <<~'LINES'
+        IRB.conf[:PROMPT][:MY_PROMPT] = {
+          :PROMPT_I => "%03n> ",
+          :PROMPT_N => "%03n> ",
+          :PROMPT_S => "%03n> ",
+          :PROMPT_C => "%03n> "
+        }
+        IRB.conf[:PROMPT_MODE] = :MY_PROMPT
+        puts 'start IRB'
+      LINES
+      start_terminal(4, 12, %W{ruby -I#{@pwd}/lib #{@pwd}/exe/irb}, startup_message: 'start IRB')
+      write("Str\C-i")
+      close
+      assert_screen(<<~EOC)
+        001> String
+        PressString
+        StrinStruct
+        of by
+      EOC
+    end
+
     private def write_irbrc(content)
       File.open(@irbrc_file, 'w') do |f|
         f.write content