Howto unit test for LOOKUP with external reference

[Regina Henschel]

Hi all,

this is about bug 167582. The fix itself is in 
https://gerrit.libreoffice.org/c/core/+/188304
But currently without unit test.

I could add the test values themselves to
sc/qa/unit/data/functions/spreadsheet/fods/lookup.fods

But were to put the source file for the external links?

Make the source file a pseudo test, so that 
sc_spreadsheet_functions_test does not fail?

Or is there another place?

Kind regards,
Regina