for testing with a release build, use
$ make tests/Fib

for testing a release build against OpenJDK output, use
$ make tests/Fib.test

for testing with a debug build, use
$ DBGFLAGS='-DDBG_JIT -DDBG_BB' make tests/Fib.dbg

`make clean' is needed if you change $DBGFLAGS.
for all available flags, see `debug.h'.