umfpacktest.cc does not compile if umfpack is present but not suitesparse
As far as I understand the test the problem is the following:
In this case the test defined SuiteSparse_UMFPACK_FOUND which activates the test.
On the other hand HAVE_SUITESPARSE_UMFPACK which is checked in our umfpack.hh is set to ENABLE_SUITESPARSE in config.h. This, however, is only set if SuiteSparse_FOUND is true.