diff --git a/include/trick/UnitTest.hh b/include/trick/UnitTest.hh
index 09e34780..00a2d49a 100644
--- a/include/trick/UnitTest.hh
+++ b/include/trick/UnitTest.hh
@@ -105,6 +105,10 @@ namespace Trick {
              */
             int set_file_name(std::string in_name) ;
 
+            /**
+             @brief Write output to xml file.
+             @return always 0
+             */
             int write_output() ;
     } ;