Guile has one testcase labeled as an external test. Compared to the other tests, this uses a different path in the makefiles: it uses swig_and_compile_external.
Looking through the rest of the swig modules, I find only the chicken module to use this as well (the chicken module looks to be very similar to the guile module in many ways).
Unfortunately, this test is failing (the external cxx file is not found). As I don't find tests in any of the more mainstream modules (like python, perl,...) using swig_and_compile_external, I'm starting to wonder if perhaps this is a deprecated swig feature, to be replaced with something else ?
So what's the story behind swig_and_compile_external ? I didn't find much by seaching the web.