From 9c455ccea583b8a190e78cae09a9696bb528f0d1 Mon Sep 17 00:00:00 2001
From: cinnaboot <cinnaboot@protonmail.com>
Date: Mon, 27 Apr 2026 13:59:43 -0400
Subject: [PATCH] refactor: true_anomaly_roundtrip - SCENARIO/SECTION pattern,
 tight tolerances

---
 tests/test_true_anomaly_roundtrip.cpp | 258 +++++++++++++-------------
 1 file changed, 134 insertions(+), 124 deletions(-)

diff --git a/tests/test_true_anomaly_roundtrip.cpp b/tests/test_true_anomaly_roundtrip.cpp
index 26f282e..7d8a908 100644
--- a/tests/test_true_anomaly_roundtrip.cpp
+++ b/tests/test_true_anomaly_roundtrip.cpp
@@ -4,130 +4,140 @@
 #include "../src/orbital_mechanics.h"
 #include <cmath>
 
-TEST_CASE("True anomaly round-trip conversion at periapsis", "[orbital_elements][true_anomaly]") {
-    double parent_mass = 5.972e24;
-
-    OrbitalElements elements = {0};
-    elements.semi_major_axis = 7000e3;
-    elements.eccentricity = 0.3;
-    elements.true_anomaly = 0.0;
-    elements.inclination = 0.0;
-    elements.longitude_of_ascending_node = 0.0;
-    elements.argument_of_periapsis = 0.0;
-
-    Vec3 pos, vel;
-    orbital_elements_to_cartesian(elements, parent_mass, &pos, &vel);
-    OrbitalElements reconstructed = cartesian_to_orbital_elements(pos, vel, parent_mass);
-
-    INFO("Original true_anomaly: " << elements.true_anomaly);
-    INFO("Reconstructed true_anomaly: " << reconstructed.true_anomaly);
-
-    REQUIRE_THAT(reconstructed.true_anomaly,
-                 Catch::Matchers::WithinAbs(elements.true_anomaly, 0.01));
+SCENARIO("True anomaly round-trip conversion preserves values",
+         "[orbital_elements][true_anomaly]") {
+    const double parent_mass = 5.972e24;
+    const double a = 7000e3;
+    const double e = 0.3;
+
+    SECTION("at periapsis (nu = 0)") {
+        const double expected_nu = 0.0;
+
+        OrbitalElements elements = {0};
+        elements.semi_major_axis = a;
+        elements.eccentricity = e;
+        elements.true_anomaly = expected_nu;
+        elements.inclination = 0.0;
+        elements.longitude_of_ascending_node = 0.0;
+        elements.argument_of_periapsis = 0.0;
+
+        Vec3 pos, vel;
+        orbital_elements_to_cartesian(elements, parent_mass, &pos, &vel);
+        OrbitalElements reconstructed = cartesian_to_orbital_elements(pos, vel, parent_mass);
+
+        INFO("Expected nu: " << expected_nu);
+        INFO("Reconstructed: " << reconstructed.true_anomaly);
+
+        REQUIRE_THAT(reconstructed.true_anomaly,
+                     Catch::Matchers::WithinAbs(expected_nu, 1e-12));
+    }
+
+    SECTION("at apoapsis (nu = pi)") {
+        const double expected_nu = M_PI;
+
+        OrbitalElements elements = {0};
+        elements.semi_major_axis = a;
+        elements.eccentricity = e;
+        elements.true_anomaly = expected_nu;
+        elements.inclination = 0.0;
+        elements.longitude_of_ascending_node = 0.0;
+        elements.argument_of_periapsis = 0.0;
+
+        Vec3 pos, vel;
+        orbital_elements_to_cartesian(elements, parent_mass, &pos, &vel);
+        OrbitalElements reconstructed = cartesian_to_orbital_elements(pos, vel, parent_mass);
+
+        INFO("Expected nu: " << expected_nu);
+        INFO("Reconstructed: " << reconstructed.true_anomaly);
+
+        REQUIRE_THAT(reconstructed.true_anomaly,
+                     Catch::Matchers::WithinAbs(expected_nu, 1e-12));
+    }
+
+    SECTION("at 90 degrees (nu = pi/2)") {
+        const double expected_nu = M_PI / 2.0;
+
+        OrbitalElements elements = {0};
+        elements.semi_major_axis = a;
+        elements.eccentricity = e;
+        elements.true_anomaly = expected_nu;
+        elements.inclination = 0.0;
+        elements.longitude_of_ascending_node = 0.0;
+        elements.argument_of_periapsis = 0.0;
+
+        Vec3 pos, vel;
+        orbital_elements_to_cartesian(elements, parent_mass, &pos, &vel);
+        OrbitalElements reconstructed = cartesian_to_orbital_elements(pos, vel, parent_mass);
+
+        INFO("Expected nu: " << expected_nu);
+        INFO("Reconstructed: " << reconstructed.true_anomaly);
+
+        REQUIRE_THAT(reconstructed.true_anomaly,
+                     Catch::Matchers::WithinAbs(expected_nu, 1e-12));
+    }
+
+    SECTION("at 270 degrees (nu = 3*pi/2)") {
+        const double expected_nu = 3.0 * M_PI / 2.0;
+
+        OrbitalElements elements = {0};
+        elements.semi_major_axis = a;
+        elements.eccentricity = e;
+        elements.true_anomaly = expected_nu;
+        elements.inclination = 0.0;
+        elements.longitude_of_ascending_node = 0.0;
+        elements.argument_of_periapsis = 0.0;
+
+        Vec3 pos, vel;
+        orbital_elements_to_cartesian(elements, parent_mass, &pos, &vel);
+        OrbitalElements reconstructed = cartesian_to_orbital_elements(pos, vel, parent_mass);
+
+        INFO("Expected nu: " << expected_nu);
+        INFO("Reconstructed: " << reconstructed.true_anomaly);
+
+        REQUIRE_THAT(reconstructed.true_anomaly,
+                     Catch::Matchers::WithinAbs(expected_nu, 1e-12));
+    }
 }
 
-TEST_CASE("True anomaly round-trip conversion at apoapsis", "[orbital_elements][true_anomaly]") {
-    double parent_mass = 5.972e24;
-
-    OrbitalElements elements = {0};
-    elements.semi_major_axis = 7000e3;
-    elements.eccentricity = 0.3;
-    elements.true_anomaly = M_PI;
-    elements.inclination = 0.0;
-    elements.longitude_of_ascending_node = 0.0;
-    elements.argument_of_periapsis = 0.0;
-
-    Vec3 pos, vel;
-    orbital_elements_to_cartesian(elements, parent_mass, &pos, &vel);
-    OrbitalElements reconstructed = cartesian_to_orbital_elements(pos, vel, parent_mass);
-
-    INFO("Original true_anomaly: " << elements.true_anomaly);
-    INFO("Reconstructed true_anomaly: " << reconstructed.true_anomaly);
-
-    REQUIRE_THAT(reconstructed.true_anomaly,
-                 Catch::Matchers::WithinAbs(elements.true_anomaly, 0.01));
-}
-
-TEST_CASE("True anomaly round-trip conversion at 90 degrees", "[orbital_elements][true_anomaly]") {
-    double parent_mass = 5.972e24;
-
-    OrbitalElements elements = {0};
-    elements.semi_major_axis = 7000e3;
-    elements.eccentricity = 0.3;
-    elements.true_anomaly = M_PI / 2.0;
-    elements.inclination = 0.0;
-    elements.longitude_of_ascending_node = 0.0;
-    elements.argument_of_periapsis = 0.0;
-
-    Vec3 pos, vel;
-    orbital_elements_to_cartesian(elements, parent_mass, &pos, &vel);
-    OrbitalElements reconstructed = cartesian_to_orbital_elements(pos, vel, parent_mass);
-
-    INFO("Original true_anomaly: " << elements.true_anomaly);
-    INFO("Reconstructed true_anomaly: " << reconstructed.true_anomaly);
-
-    REQUIRE_THAT(reconstructed.true_anomaly,
-                 Catch::Matchers::WithinAbs(elements.true_anomaly, 0.01));
-}
-
-TEST_CASE("True anomaly round-trip conversion at 270 degrees", "[orbital_elements][true_anomaly]") {
-    double parent_mass = 5.972e24;
-
-    OrbitalElements elements = {0};
-    elements.semi_major_axis = 7000e3;
-    elements.eccentricity = 0.3;
-    elements.true_anomaly = 3.0 * M_PI / 2.0;
-    elements.inclination = 0.0;
-    elements.longitude_of_ascending_node = 0.0;
-    elements.argument_of_periapsis = 0.0;
-
-    Vec3 pos, vel;
-    orbital_elements_to_cartesian(elements, parent_mass, &pos, &vel);
-    OrbitalElements reconstructed = cartesian_to_orbital_elements(pos, vel, parent_mass);
-
-    INFO("Original true_anomaly: " << elements.true_anomaly);
-    INFO("Reconstructed true_anomaly: " << reconstructed.true_anomaly);
-
-    REQUIRE_THAT(reconstructed.true_anomaly,
-                 Catch::Matchers::WithinAbs(elements.true_anomaly, 0.01));
-}
-
-TEST_CASE("Radius at periapsis matches expected value", "[orbital_elements][sanity]") {
-    double parent_mass = 5.972e24;
-
-    OrbitalElements peri = {0};
-    peri.semi_major_axis = 7000e3;
-    peri.eccentricity = 0.3;
-    peri.true_anomaly = 0.0;
-
-    Vec3 pos, vel;
-    orbital_elements_to_cartesian(peri, parent_mass, &pos, &vel);
-    double r_peri = vec3_magnitude(pos);
-    double expected_peri = peri.semi_major_axis * (1.0 - peri.eccentricity);
-
-    INFO("At true_anomaly=0:");
-    INFO("  Calculated radius: " << r_peri);
-    INFO("  Expected: " << expected_peri);
-
-    REQUIRE_THAT(r_peri, Catch::Matchers::WithinAbs(expected_peri, 1.0));
-}
-
-TEST_CASE("Radius at apoapsis matches expected value", "[orbital_elements][sanity]") {
-    double parent_mass = 5.972e24;
-
-    OrbitalElements apo = {0};
-    apo.semi_major_axis = 7000e3;
-    apo.eccentricity = 0.3;
-    apo.true_anomaly = M_PI;
-
-    Vec3 pos, vel;
-    orbital_elements_to_cartesian(apo, parent_mass, &pos, &vel);
-    double r_apo = vec3_magnitude(pos);
-    double expected_apo = apo.semi_major_axis * (1.0 + apo.eccentricity);
-
-    INFO("At true_anomaly=pi:");
-    INFO("  Calculated radius: " << r_apo);
-    INFO("  Expected: " << expected_apo);
-
-    REQUIRE_THAT(r_apo, Catch::Matchers::WithinAbs(expected_apo, 1.0));
+SCENARIO("Radius at periapsis and apoapsis matches analytical formula",
+         "[orbital_elements][sanity]") {
+    const double parent_mass = 5.972e24;
+    const double a = 7000e3;
+    const double e = 0.3;
+    const double expected_r_peri = a * (1.0 - e);  // 4900000.0
+    const double expected_r_apo = a * (1.0 + e);   // 9100000.0
+
+    SECTION("periapsis radius = a*(1-e)") {
+        OrbitalElements peri = {0};
+        peri.semi_major_axis = a;
+        peri.eccentricity = e;
+        peri.true_anomaly = 0.0;
+
+        Vec3 pos, vel;
+        orbital_elements_to_cartesian(peri, parent_mass, &pos, &vel);
+        const double r_peri = vec3_magnitude(pos);
+
+        INFO("Expected r: " << expected_r_peri);
+        INFO("Calculated r: " << r_peri);
+
+        REQUIRE_THAT(r_peri,
+                     Catch::Matchers::WithinAbs(expected_r_peri, 1e-6));
+    }
+
+    SECTION("apoapsis radius = a*(1+e)") {
+        OrbitalElements apo = {0};
+        apo.semi_major_axis = a;
+        apo.eccentricity = e;
+        apo.true_anomaly = M_PI;
+
+        Vec3 pos, vel;
+        orbital_elements_to_cartesian(apo, parent_mass, &pos, &vel);
+        const double r_apo = vec3_magnitude(pos);
+
+        INFO("Expected r: " << expected_r_apo);
+        INFO("Calculated r: " << r_apo);
+
+        REQUIRE_THAT(r_apo,
+                     Catch::Matchers::WithinAbs(expected_r_apo, 1e-6));
+    }
 }