add test case to verify spacecraft state vectors

tests/test_maneuvers.cpp

@@ -159,3 +159,74 @@ TEST_CASE("Spacecraft propagation maintains stability", "[spacecraft][propagatio
 
     destroy_simulation(sim);
 }
+
+TEST_CASE("Spacecraft state vectors at orbital quarters", "[spacecraft][state_vectors]") {
+    const double TIME_STEP = 60.0;
+
+    SimulationState* sim = create_simulation(10, 10, 0, TIME_STEP);
+
+    REQUIRE(load_system_config(sim, "tests/test_maneuvers.toml"));
+
+    Spacecraft* craft = &sim->spacecraft[0];
+    CelestialBody* earth = &sim->bodies[1];
+
+    double orbit_radius = vec3_magnitude(craft->local_position);
+    double earth_mass = earth->mass;
+
+    double orbital_period = 2.0 * M_PI * sqrt(pow(orbit_radius, 3.0) / (G * earth_mass));
+    double quarter_orbit_time = orbital_period / 4.0;
+    int steps_per_quarter = (int)(quarter_orbit_time / TIME_STEP);
+
+    INFO("Orbital radius: " << orbit_radius << " m");
+    INFO("Expected orbital period: " << orbital_period << " s (" << orbital_period / 3600.0 << " hours)");
+    INFO("Steps per quarter: " << steps_per_quarter);
+
+    double previous_angle = atan2(craft->local_position.y, craft->local_position.x);
+
+    for (int quarter = 0; quarter <= 4; quarter++) {
+        INFO("");
+        INFO("=== Point " << quarter << "/4 (" << (quarter * 90) << "°) ===");
+        INFO("Local position: (" << craft->local_position.x << ", " << craft->local_position.y << ", " << craft->local_position.z << ") m");
+        INFO("Local velocity: (" << craft->local_velocity.x << ", " << craft->local_velocity.y << ", " << craft->local_velocity.z << ") m/s");
+
+        double current_radius = vec3_magnitude(craft->local_position);
+        double current_velocity = vec3_magnitude(craft->local_velocity);
+        double current_angle = atan2(craft->local_position.y, craft->local_position.x);
+
+        INFO("Radius: " << current_radius << " m");
+        INFO("Velocity magnitude: " << current_velocity << " m/s");
+        INFO("Angular position: " << current_angle << " rad (" << (current_angle * 180.0 / M_PI) << "°)");
+
+        if (quarter > 0) {
+            double angle_change = current_angle - previous_angle;
+            if (angle_change < 0) angle_change += 2.0 * M_PI;
+            INFO("Angle change from previous: " << angle_change << " rad (" << (angle_change * 180.0 / M_PI) << "°)");
+            REQUIRE(fabs(angle_change - M_PI / 2.0) < 0.1);
+        }
+
+        if (quarter < 4) {
+            for (int step = 0; step < steps_per_quarter; step++) {
+                update_simulation(sim);
+            }
+        }
+
+        previous_angle = current_angle;
+    }
+
+    INFO("");
+    INFO("=== Final Summary ===");
+    double final_radius = vec3_magnitude(craft->local_position);
+    double final_velocity = vec3_magnitude(craft->local_velocity);
+    double final_angle = atan2(craft->local_position.y, craft->local_position.x);
+    double total_rotation = final_angle;
+
+    if (total_rotation < 0) total_rotation += 2.0 * M_PI;
+
+    INFO("Total rotation: " << total_rotation << " rad (" << (total_rotation * 180.0 / M_PI) << "°)");
+    INFO("Radius change: " << ((final_radius - orbit_radius) / orbit_radius * 100.0) << "%");
+    INFO("Velocity change: " << ((final_velocity - vec3_magnitude(craft->local_velocity)) / vec3_magnitude(craft->local_velocity) * 100.0) << "%");
+
+    REQUIRE(fabs(total_rotation - 2.0 * M_PI) < 0.1);
+
+    destroy_simulation(sim);
+}