How do I do calculations with the last and first array member in a for loop?

for example, I want to show another matrix that its elements are the sum of consecutive members in the original array, and the last showing the sum of the last with the first element, without explicitly managing the last case.

test = [1 2 3];

consecutiveSum = [ test(1) + test(2) , test(2) + test(3) , test(3) + test(1) ];

How can I implement this in a for loop?

Answer 1

[the cyclist]

test = [1 2 3];
N = numel(test);
idx = [1:N; [2:N,1]];
consecutiveSum = sum(test(idx));