diff --git a/apps/CMakeLists.txt b/apps/CMakeLists.txt
index 8001080..a98e572 100644
--- a/apps/CMakeLists.txt
+++ b/apps/CMakeLists.txt
@@ -7,4 +7,4 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 add_executable(chapter_05 chapter_05.cpp)
 
-target_link_libraries(chapter_05 PRIVATE raytracing)
+target_link_libraries(chapter_05 PRIVATE raytracing gcov)
diff --git a/raytracing/CMakeLists.txt b/raytracing/CMakeLists.txt
index ebf7be1..8407a0e 100644
--- a/raytracing/CMakeLists.txt
+++ b/raytracing/CMakeLists.txt
@@ -1,9 +1,11 @@
 cmake_minimum_required(VERSION 3.14)
 
+project(raytracing)
+
 set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
-project(raytracing)
+add_definitions(--coverage)
 
 add_library(raytracing
 
diff --git a/raytracing/src/object.cpp b/raytracing/src/object.cpp
index 64bfb49..04cb7cc 100644
--- a/raytracing/src/object.cpp
+++ b/raytracing/src/object.cpp
@@ -103,6 +103,14 @@ void Object::set_transform(const Matrix &a_transform_matrix)
 
 /* ------------------------------------------------------------------------- */
 
+Tuple Object::normal_at(const Tuple &a_point)
+{
+    Tuple the_result = a_point - Tuple::Point(0, 0, 0);
+    return the_result.normalize();
+}
+
+/* ------------------------------------------------------------------------- */
+
 Intersections Object::intersect(Ray &a_ray)
 {
     Intersections the_ret;
diff --git a/raytracing/src/object.h b/raytracing/src/object.h
index 8fd71e6..5bba391 100644
--- a/raytracing/src/object.h
+++ b/raytracing/src/object.h
@@ -56,6 +56,8 @@ namespace Raytracer
         Matrix &transform(void);
         void set_transform(const Matrix &a_transform_matrix);
 
+        Tuple normal_at(const Tuple &a_point);
+
         virtual Intersections intersect(Ray &a_ray);
 
     protected:
diff --git a/tests/06_light_shading.cpp b/tests/06_light_shading.cpp
index aec573b..d9776d7 100644
--- a/tests/06_light_shading.cpp
+++ b/tests/06_light_shading.cpp
@@ -37,10 +37,13 @@ SCENARIO("The normal on a sphere at point a on the x axis", "[features/spheres.f
 {
     GIVEN("s <- sphere()")
     {
+        Sphere s;
         WHEN("n <- normal_at(s, point(1,0,0))")
         {
+            Tuple n = s.normal_at(Tuple::Point(1, 0, 0));
             THEN("n = vector(1,0,0)")
             {
+                REQUIRE(n == Tuple::Vector(1, 0, 0));
             }
         }
     }
@@ -52,10 +55,13 @@ SCENARIO("The normal on a sphere at point a on the y axis", "[features/spheres.f
 {
     GIVEN("s <- sphere()")
     {
+        Sphere s;
         WHEN("n <- normal_at(s, point(0,1,0))")
         {
+            Tuple n = s.normal_at(Tuple::Point(0, 1, 0));
             THEN("n = vector(0,1,0)")
             {
+                REQUIRE(n == Tuple::Vector(0, 1, 0));
             }
         }
     }
@@ -67,10 +73,13 @@ SCENARIO("The normal on a sphere at point a on the z axis", "[features/spheres.f
 {
     GIVEN("s <- sphere()")
     {
+        Sphere s;
         WHEN("n <- normal_at(s, point(0,0,1))")
         {
+            Tuple n = s.normal_at(Tuple::Point(0, 0, 1));
             THEN("n = vector(0,0,1)")
             {
+                REQUIRE(n == Tuple::Vector(0, 0, 1));
             }
         }
     }
@@ -82,10 +91,13 @@ SCENARIO("The normal on a sphere at a nonaxial point", "[features/spheres.featur
 {
     GIVEN("s <- sphere()")
     {
+        Sphere s;
         WHEN("n <- normal_at(s, point(sqrt(3)/3,sqrt(3)/3,sqrt(3)/3))")
         {
-            THEN("n = vector(sqrt(3)/3,sqrt(3)/3,sqrt(3)/3)")
+            Tuple n = s.normal_at(Tuple::Point(sqrt(3) / 3, sqrt(3) / 3, sqrt(3) / 3));
+            THEN("n = vector(sqrt(3)/3,sqrt(3)/3,sqrt(3)/3))")
             {
+                REQUIRE(n == Tuple::Vector(sqrt(3) / 3, sqrt(3) / 3, sqrt(3) / 3));
             }
         }
     }
@@ -97,10 +109,13 @@ SCENARIO("The normal is a normalized vector", "[features/spheres.feature]")
 {
     GIVEN("s <- sphere()")
     {
+        Sphere s;
         WHEN("n <- normal_at(s, point(sqrt(3)/3,sqrt(3)/3,sqrt(3)/3))")
         {
+            Tuple n = s.normal_at(Tuple::Point(sqrt(3) / 3, sqrt(3) / 3, sqrt(3) / 3));
             THEN("n = normalize(n)")
             {
+                REQUIRE(n == n.normalize());
             }
         }
     }
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 478fbd4..7148328 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -21,4 +21,6 @@ add_executable(raytracing_test
 
 include_directories("${CMAKE_SOURCE_DIR}/tests")
 
-target_link_libraries(raytracing_test PRIVATE raytracing)
+target_link_libraries(raytracing_test PRIVATE raytracing gcov)
+
+add_test(NAME raytracing_test COMMAND tests/raytracing_test)