1 unit_test_equals("zero order divided_difference_coefficients", ...
3 divided_difference_coefficients([0]));
5 unit_test_equals("first order divided_difference_coefficients", ...
7 divided_difference_coefficients([0, pi]));
9 unit_test_equals("second order divided_difference_coefficients", ...
10 [1, -2, 1] / (2*pi^2), ...
11 divided_difference_coefficients([0, pi, 2*pi]));