Add test/Kernel_23/test_approximate_dihedral_angle_3.cpp

Kernel_23/test/Kernel_23/test_approximate_dihedral_angle_3.cpp

@@ -0,0 +1,36 @@
+#include <CGAL/Simple_cartesian.h>
+#include <CGAL/Kernel/global_functions_3.h>
+#include <iostream>
+#include <utility>
+using K = CGAL::Simple_cartesian<double>;
+using Point_3 = K::Point_3;
+
+struct query {
+  Point_3 p;
+  double expected_angle;
+};
+
+int main() {
+  Point_3 a = {0, 0, 0};
+  Point_3 b = {0, 1, 0};
+  Point_3 c = {1, 0, 0};
+
+  const query queries[] = {
+    { {  1, 0,  0},    0.},
+    { {  1, 0,  1},   45.},
+    { {  0, 0,  1},   90.},
+    { { -1, 0,  1},  135.},
+    { { -1, 0,  0},  180.},
+    { { -1, 0, -1}, -135.},
+    { {  0, 0, -1},  -90.},
+    { {  1, 0, -1},  -45.},
+  };
+
+  for(auto query: queries) {
+    const auto& expected = query.expected_angle;
+    const auto& p = query.p;
+    auto approx = CGAL::approximate_dihedral_angle(a, b, c, p);
+    std::cout << approx << "  -- " << expected << '\n';
+    assert( std::abs(approx - expected) < 0.1 );
+  }
+};