For a while now "make test" fails here in the testIo step
It looks like a lock issue; in gdb I see
(gdb) list
247         csoundCompileOrc(csound, instrument);
248         csoundReadScore(csound, "i 1 0 0.1\n e 0.2");
249     //    csoundSetMIDIModule(csound, "hostbased");
250         csoundSetHostImplementedMIDIIO(csound, 1);
251         csoundSetOutput(csound, "dac", NULL, NULL);
252         int ret = csoundStart(csound);
253         CU_ASSERT(ret == 0);
254         ret = csoundPerform(csound);
255         CU_ASSERT(ret > 0);
256         csoundReset(csound);
(gdb) where
#0  0x00007ffff774e79c in __lll_lock_wait () from /lib64/libpthread.so.0
#1  0x00007ffff774a489 in _L_lock_909 () from /lib64/libpthread.so.0
#2  0x00007ffff774a2b0 in pthread_mutex_lock () from /lib64/libpthread.so.0
#3  0x00007fffe8232546 in csound_global_mutex_lock ()
    at /home/jpff/csound6/./H/csGblMtx.h:44
#4  start_portmidi (csound=0x897780) at /home/jpff/csound6/InOut/pmidi.c:153
#5  listDevices (csound=0x897780, list=0xa677a0, isOutput=1)
    at /home/jpff/csound6/InOut/pmidi.c:183
#6  0x0000000000409e95 in test_dev_list ()
    at /home/jpff/csound6/tests/c/io_test.c:29
#7  0x00007ffff7bce261 in ?? () from /usr/lib64/libcunit.so.1
#8  0x00007ffff7bce56f in ?? () from /usr/lib64/libcunit.so.1
#9  0x00007ffff7bce8a6 in CU_run_all_tests () from /usr/lib64/libcunit.so.1
#10 0x0000000000409c8b in main (argc=, argv=)
    at /home/jpff/csound6/tests/c/io_test.c:290