1 files changed, 17 insertions, 0 deletions
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index 0325867496..c62edbba00 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -1975,4 +1975,21 @@ End
     write_file.close
     file.close!
   end
+
+  def test_warn
+    stderr = EnvUtil.verbose_warning do
+      warn "warning"
+    end
+    assert_equal("warning\n", stderr)
+
+    stderr = EnvUtil.verbose_warning do
+      warn
+    end
+    assert_equal("", stderr)
+
+    stderr = EnvUtil.verbose_warning do
+      warn "[Feature #5029]", "[ruby-core:38070]"
+    end
+    assert_equal("[Feature #5029]\n[ruby-core:38070]\n", stderr)
+  end
 end