I fixed the tests last fall according to what I consider the right way to
do tests like this. As I have said several times before tests should not
in general use absolute tolerances, rather they should take into account
the size of the data. So for example instead of
assert (fftfilt (b, r * x),r * r * [1, 1, 0, 0, 0, 0, 0, 0, 0, 0],eps)
I used
%! y = r*r*[1 1 0 0 0 0 0 0 0 0];
%! tol = 2*norm(y)*eps;
%! assert (fftfilt (b, r*x), y, tol);
There are a number of tests like this (eig.cc for example) with absolute
tolerances which should be using norms. But don't take my word for it,
see, e.g. Golub & Van Loan, "Matrix Computations".