1 files changed, 16 insertions, 0 deletions
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index f456779880..69e3666cff 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -118,6 +118,22 @@ class TestIO < Test::Unit::TestCase
     r.close
   end
 
+  def test_ungetbyte
+    t = make_tempfile
+    t.open
+    t.ungetbyte(0x41)
+    assert_equal(0x41, t.getbyte)
+    t.rewind
+    t.ungetbyte("qux")
+    assert_equal("quxfoo\n", t.gets)
+    t.set_encoding("utf-8")
+    t.ungetbyte(0x89)
+    t.ungetbyte(0x8e)
+    t.ungetbyte("\xe7")
+    t.ungetbyte("\xe7\xb4\x85")
+    assert_equal("\u7d05\u7389bar\n", t.gets)
+  end
+
   def test_each_byte
     r, w = IO.pipe
     w << "abc def"