1 files changed, 8 insertions, 0 deletions
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index a1462c53b2..ea1dfc758c 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -3555,6 +3555,14 @@ __END__
     end
   end if File::BINARY != 0
 
+  def test_exclusive_mode
+    make_tempfile do |t|
+      assert_raise(Errno::EEXIST){ open(t.path, 'wx'){} }
+      assert_raise(ArgumentError){ open(t.path, 'rx'){} }
+      assert_raise(ArgumentError){ open(t.path, 'ax'){} }
+    end
+  end
+
   def test_race_gets_and_close
     assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
     bug13076 = '[ruby-core:78845] [Bug #13076]'