fix(FinalGradeDeterminator): Add mock class for DatabaseManger

The mock class is used to bypass the blocking error of the
FinalGradeDeterminator when no Database is present for testing purposes

src/g2_2025_grade_calculator_pkg/test/FinalGradeDeterminator.test.cpp

@@ -12,6 +12,36 @@
 using namespace std::chrono_literals;
 using namespace assignments::one::final_grade_determinator;
 
+namespace assignments::one {
+
+class FakeDatabaseManager : public DatabaseManager {
+public:
+    explicit FakeDatabaseManager(rclcpp::Logger logger = rclcpp::get_logger("fake_db"))
+        : DatabaseManager(logger) {}
+
+    bool is_connected() const override {
+        return true; // Always pretend we are connected
+    }
+
+    bool store_final_course_result(const StudentCourse& sc, int exam_count, int final_grade) override {
+        stored_results_.push_back({sc, exam_count, final_grade});
+        return true; // Always succeed
+    }
+
+    void init_database() override {
+        // No-op for fake
+    }
+
+    struct StoredResult {
+        StudentCourse sc;
+        int exam_count;
+        int final_grade;
+    };
+    std::vector<StoredResult> stored_results_;
+};
+
+} // namespace assignments::one
+
 class FinalGradeDeterminatorTest : public ::testing::Test {
 protected:
     void SetUp() override {
@@ -53,12 +83,14 @@ protected:
 
     void TearDown() override {
         final_grade_determinator_.reset();
+        fake_db_.reset();
         test_node_.reset();
         rclcpp::shutdown();
     }
 
     void create_final_grade_determinator() {
-        final_grade_determinator_ = std::make_shared<FinalGradeDeterminator>();
+        fake_db_ = std::make_unique<assignments::one::FakeDatabaseManager>();
+        final_grade_determinator_ = std::make_shared<FinalGradeDeterminator>(std::move(fake_db_));
     }
 
     void spin_some_time(std::chrono::milliseconds duration = 100ms) {
@@ -71,13 +103,12 @@ protected:
             std::this_thread::sleep_for(10ms);
         }
     }
-
+    std::unique_ptr<assignments::one::FakeDatabaseManager> fake_db_;
     std::shared_ptr<rclcpp::Node> test_node_;
     std::shared_ptr<FinalGradeDeterminator> final_grade_determinator_;
     rclcpp::Subscription<g2_2025_interfaces::msg::Student>::SharedPtr student_subscriber_;
     rclcpp::Publisher<g2_2025_interfaces::msg::Exam>::SharedPtr exam_publisher_;
     rclcpp::Service<g2_2025_interfaces::srv::Exams>::SharedPtr grade_calculator_service_;
-
     std::vector<g2_2025_interfaces::msg::Student> received_student_messages_;
     std::vector<g2_2025_interfaces::srv::Exams::Request> service_requests_;
 };