add test to completion

Library/Contributions/brew_bash_completion.sh

@@ -35,7 +35,7 @@ _brew_to_completion()
         return
         ;;
     # Commands that take an existing brew
-    abv|cleanup|link|list|ln|ls|remove|rm|uninstall|unlink)
+    abv|cleanup|link|list|ln|ls|remove|rm|test|uninstall|unlink)
         COMPREPLY=( $(compgen -W "$(\ls $(brew --cellar))" -- ${cur}) )
         return
         ;;