1 files changed, 12 insertions, 0 deletions
diff --git a/mrbgems/mruby-string-ext/test/string.rb b/mrbgems/mruby-string-ext/test/string.rb
index a5d55a7ee..228a236af 100644
--- a/mrbgems/mruby-string-ext/test/string.rb
+++ b/mrbgems/mruby-string-ext/test/string.rb
@@ -30,6 +30,18 @@ assert('String#setbyte') do
   assert_equal("Hello", str1)
 end
 
+assert("String#setbyte raises IndexError if arg conversion resizes String") do
+  $s = "01234\n"
+  class Tmp
+      def to_i
+          $s.chomp! ''
+          95
+      end
+  end
+  tmp = Tmp.new
+  assert_raise(IndexError) { $s.setbyte(5, tmp) }
+end
+
 assert('String#byteslice') do
   str1 = "hello"
   assert_equal("e", str1.byteslice(1))