1 files changed, 24 insertions, 1 deletions
diff --git a/mrbgems/mruby-sprintf/test/sprintf.rb b/mrbgems/mruby-sprintf/test/sprintf.rb
index 454c226e1..ccbd95d51 100644
--- a/mrbgems/mruby-sprintf/test/sprintf.rb
+++ b/mrbgems/mruby-sprintf/test/sprintf.rb
@@ -5,5 +5,28 @@ assert('String#%') do
   assert_equal "one=1", "one=%d" % 1
   assert_equal "1 one 1.0", "%d %s %3.1f" % [ 1, "one", 1.01 ]
   assert_equal "123 < 456", "%{num} < %<str>s" % { num: 123, str: "456" }
-  assert_equal 16, ("%b" % (1<<15)).size
+  assert_equal 15, ("%b" % (1<<14)).size
+end
+
+assert("String#% with invalid chr") do
+  begin
+    class Fixnum
+      alias_method :chr_, :chr if method_defined?(:chr)
+
+      def chr
+        nil
+      end
+    end
+
+    assert_raise TypeError do
+      "%c" % 0
+    end
+  ensure
+    class Fixnum
+      if method_defined?(:chr_)
+        alias_method :chr, :chr_
+        remove_method :chr_
+      end
+    end
+  end
 end