function success = testclose(x, y, tol)
%TESTCLOSE verbosely check two inputs are close. Use in test cases.
%
% success = testclose(x, y, tol)
% checks whether max fractional difference is less than tolerance:
%     max(abs(x(:)-y(:)))./abs(min(x(:), y(:))) < tol.
%
% This function is verbose, outputting a result suitable for use in test cases.
% Also returns true/false for further processing, e.g. assert(testclose(...)) to
% force stopping a test case.
%
% tol = 1e-9 by default

% Iain Murray, November 2007, September 2010

if nargin < 3
    tol = 1e-9;
end

assert(tol >= 0);

% Annoying special cases
if ~isequal(size(x), size(y))
    success = false;
    fprintf('FAILURE: matrices are not the same size\n');
    return;
end
if isempty(x)
    success = true;
    fprintf('OK          (matrices are both empty and of the same size)\n');
    return
end

nanx = isnan(x);
if ~isequal(nanx, isnan(y))
    success = false;
    fprintf('FAILURE: Some values were NaN only in one of the arrays.\n');
    return
end
idx = (x ~= y) & ~nanx;
if any(idx)
    max_err = max(abs(x(idx) - y(idx))./min(abs(x(idx)), abs(y(idx))));
else
    max_err = 0;
end
success = max_err < tol;

if success
    fprintf('OK          (fractional difference of %0.3g < (tol=%0.3g))\n', max_err, tol);
else
    fprintf('FAILURE: fractional difference of %0.3g exceeds tolerance of %0.3g\n', max_err, tol);
end
if any(nanx)
    fprintf('WARNING: some of the values tested were NaNs\n');
end