mkdir testDir;  cd testDir

fid = fopen ('PKG_ADD', 'w');
fprintf (fid, 'x = 33\n');
fclose (fid);

fid = fopen ('PKG_DEL', 'w');
fprintf (fid, 'x = x * 3\n');
fclose (fid);

cd ..

addpath testDir
rmpath testDir

assert (x == 99)