Add WORKING_DIRECTORY open question

Help/ctest_alt_dir.rst

@@ -122,6 +122,17 @@ directory it should start generating it, because that's different from
 adding global state similar to :variable:`CMAKE_BINARY_DIR`, e.g.
 :variable:`CMAKE_CTEST_DIR` or :variable:`CMAKE_TEST_DIR`.
 
+Open Questions
+==============
+
+#. How does :prop_test:`WORKING_DIRECTORY`'s value get interpreted and used?
+ * Can it contain a path relative to the current ``CTestTestfile.cmake``'s
+   containing directory?
+#. How do relative paths in :prop_test:`ATTACHED_FILES`,
+   :prop_test:`ATTACHED_FILES_ON_FAIL` and the :prop_test:`REQUIRED_FILES` test
+   properties get interpreted?
+ * Is it relative to :prop_test:`WORKING_DIRECTORY`?
+
 Non-goals
 =========