1 files changed, 13 insertions, 0 deletions
diff --git a/test/psych/test_string.rb b/test/psych/test_string.rb
index 20ab79c05a..84ae5cbb45 100644
--- a/test/psych/test_string.rb
+++ b/test/psych/test_string.rb
@@ -17,6 +17,19 @@ module Psych
       end
     end
 
+    # 'y', 'Y', 'n', 'N' are kind of ambiguous.  Syck treated those literals in
+    # YAML documents as strings.  But this is not what the YAML 1.1 spec says.
+    # YAML 1.1 says they should be treated as booleans.  When we're dumping
+    # documents, we know it's a string, so adding quotes will eliminate the
+    # "ambiguity" in the emitted document
+
+    def test_all_yaml_1_1_booleans_are_quoted
+      yaml_1_1_booleans = %w[y Y yes Yes YES n N no No NO true True TRUE false False FALSE on On ON off Off OFF] # from https://yaml.org/type/bool.html
+      yaml_1_1_booleans.each do |boolean|
+        assert_match(/"#{boolean}"|'#{boolean}'/, Psych.dump(boolean))
+      end
+    end
+
     def test_string_with_newline
       assert_equal "1\n2", Psych.load("--- ! '1\n\n  2'\n")
     end