Version 0.15.1 (http://ftp.gnu.org/gnu/gnunet/gnunet-0.15.1.tar.gz) does not compile due to a missing file (src/testing/testing_cmds.h).
CC testing_api_cmd_local_test_finished.lo
testing_api_cmd_local_test_finished.c:29:10: fatal error: testing_cmds.h: No such file or directory
29 | #include "testing_cmds.h"
| ^~~~~~~~~~~~~~~~
compilation terminated.
The same does not happen instead while building the tagged commit from the git repository (https://git.gnunet.org/gnunet.git/commit/?h=v0.15.1). This probably means that the new files have not been not listed in some of Makefile.am files (most likely), or whoever created the tarball launched make dist after launching the configure script with the wrong settings (less likely).