"yes" must be in quotes to be XML compatible

tests/FILEFORMAT

@@ -275,7 +275,7 @@ off the trailing newline of this given data before comparing with the one
 actually sent by the client
 Variables are substituted as in the <command> section.
 </protocol>
-<stdout [mode="text"] [nonewline=yes]>
+<stdout [mode="text"] [nonewline="yes"]>
 This verifies that this data was passed to stdout.
 
 Use the mode="text" attribute if the output is in text mode on platforms that