[ADD] add a skeleton of the group and refactor some test datas.

tests/09_planes.cpp

@@ -31,38 +31,12 @@
 
 #include "raytracing.h"
 
+#include "common_data.h"
+
 using namespace Raytracer;
 
 /* ------------------------------------------------------------------------- */
 
-class TestShape : public Shape
-{
-public:
-    TestShape(void) = default;
-
-    Intersections local_intersect(const Ray &a_ray) override
-    {
-        saved_ray = a_ray;
-        return Intersections();
-    }
-
-    Tuple local_normal_at(const Tuple &a_local_point) const override
-    {
-        return Tuple::Vector(a_local_point.x(), a_local_point.y(), a_local_point.z());
-    }
-
-    Ray saved_ray;
-};
-
-/* ------------------------------------------------------------------------- */
-
-TestShape test_shape(void)
-{
-    return TestShape();
-}
-
-/* ------------------------------------------------------------------------- */
-
 SCENARIO("The default transformation", "[features/shapes.feature]")
 {
     GIVEN("s <- test_shape()")