1  use <angle_between.scad>
 2  
 3  module test_angle_between() {
 4      echo("==== test_angle_between  ====");
 5      assert(angle_between([0, 1], [1, 0]) == 90);
 6      assert(angle_between([0, 1, 0], [1, 0, 0]) == 90);
 7      assert(round(angle_between([1, 1, 0], [1, 1, sqrt(2)])) == 45);
 8  }
 9  
10  test_angle_between();