refactor: improve test_analytical_propagation.cpp — merge redundant SECTIONs, fix names, remove unused constant

tests/test_analytical_propagation.cpp

@@ -36,9 +36,8 @@ SCENARIO("Analytical propagation: apsides, periods, vis-viva, timestep accuracy,
     const double A2_V_PERI = 7874.183374942587e+00;  // m/s at perigee
     const double A2_V_APO = 3374.650017832537e+00;  // m/s at apogee
 
-    // Precalculated displacement for 0.1s timestep (from precalc script)
+    // 100-period propagation accumulates ~1.1e-12 rad anomaly error;
-    const double VEL_CHANGE_SMALL_DT = 0.4920854266;
+    // ANG_TOL (1e-12) is too tight for long-term stability tests
-
     const double LONG_TERM_ANG_TOL = 1e-10;
 
     // === Helper lambdas ===
@@ -148,7 +147,7 @@ SCENARIO("Analytical propagation: apsides, periods, vis-viva, timestep accuracy,
                              "Apsides spacecraft apogee");
     }
 
-    SECTION("apsides perigee velocity > apogee velocity") {
+    SECTION("apsides perigee velocity matches precalculated value") {
         Vec3 pos_peri, vel_peri, pos_apo, vel_apo;
         get_state(A1_A, A1_E, 0.0, pos_peri, vel_peri);
         get_state(A1_A, A1_E, M_PI, pos_apo, vel_apo);
@@ -160,7 +159,7 @@ SCENARIO("Analytical propagation: apsides, periods, vis-viva, timestep accuracy,
         REQUIRE_THAT(v_apo, WithinAbs(A1_V_APO, V_TOL));
     }
 
-    SECTION("apsides perigee velocity > velocity at pi/4") {
+    SECTION("apsides velocity at pi/4 matches precalculated value") {
         Vec3 pos_45, vel_45, pos_peri, vel_peri;
         get_state(A1_A, A1_E, M_PI / 4.0, pos_45, vel_45);
         get_state(A1_A, A1_E, 0.0, pos_peri, vel_peri);
@@ -182,7 +181,7 @@ SCENARIO("Analytical propagation: apsides, periods, vis-viva, timestep accuracy,
                              "Timestep spacecraft apogee");
     }
 
-    SECTION("timestep perigee velocity > apogee velocity") {
+    SECTION("timestep perigee velocity matches precalculated value") {
         Vec3 pos_peri, vel_peri, pos_apo, vel_apo;
         get_state(A2_A, A2_E, 0.0, pos_peri, vel_peri);
         get_state(A2_A, A2_E, M_PI, pos_apo, vel_apo);
@@ -216,14 +215,9 @@ SCENARIO("Analytical propagation: apsides, periods, vis-viva, timestep accuracy,
     }
 
     // --- 3. Period return (both spacecraft) ---
-    SECTION("apsides position returns after one period") {
+    SECTION("apsides position and velocity return after one period") {
-        check_period_return(A1_A, A1_E, A1_PERIOD,
-                            "Apsides spacecraft position");
-    }
-
-    SECTION("apsides velocity returns after one period") {
         check_period_return(A1_A, A1_E, A1_PERIOD,
-                            "Apsides spacecraft velocity");
+                            "Apsides spacecraft");
     }
 
     SECTION("apsides true anomaly returns after one period") {
@@ -231,14 +225,9 @@ SCENARIO("Analytical propagation: apsides, periods, vis-viva, timestep accuracy,
                              "Apsides spacecraft nu");
     }
 
-    SECTION("timestep position returns after one period") {
+    SECTION("timestep position and velocity return after one period") {
-        check_period_return(A2_A, A2_E, A2_PERIOD,
-                            "Timestep spacecraft position");
-    }
-
-    SECTION("timestep velocity returns after one period") {
         check_period_return(A2_A, A2_E, A2_PERIOD,
-                            "Timestep spacecraft velocity");
+                            "Timestep spacecraft");
     }
 
     SECTION("timestep true anomaly returns after one period") {
@@ -287,7 +276,7 @@ SCENARIO("Analytical propagation: apsides, periods, vis-viva, timestep accuracy,
         INFO("vel_change: " << vel_change << " m/s");
 
         REQUIRE_THAT(rel_pos_error, WithinAbs(0.0, REL_TOL * 100.0));
-        REQUIRE_THAT(vel_change, WithinAbs(VEL_CHANGE_SMALL_DT, V_TOL));
+        REQUIRE_THAT(vel_change, WithinAbs(0.4920854266, V_TOL));
     }
 
     SECTION("accuracy at 1x period") {