1 files changed, 3 insertions, 0 deletions
diff --git a/test/io.rb b/test/io.rb
index 955481b9f..9ce8985f7 100644
--- a/test/io.rb
+++ b/test/io.rb
@@ -234,6 +234,9 @@ assert('IO.sysopen, IO#sysread') do
     io.sysread(10000)
   end
   io.close
+  assert_equal "", io.sysread(0)
+  assert_raise(IOError) { io.sysread(1) }
+  assert_raise(ArgumentError) { io.sysread(-1) }
   io.closed?
 end