```factor
! Copyright (C) 2008 Your name.
! See http://factorcode.org/license.txt for BSD license.
USING: tools.test io.files.listing strings kernel ;
IN: io.files.listing.tests

[ ] [ "" directory. ] unit-test
```

Add unit test to assert that directory. can infeR
user
```factor
! Copyright (C) 2008 Your name.
! See http://factorcode.org/license.txt for BSD license.
USING: tools.test io.files.listing strings kernel ;
IN: io.files.listing.tests

\ directory. must-infer

[ ] [ "" directory. ] unit-test
```
assistant