refactor: rewrite test_orbital_period with SCENARIO/SECTION pattern

- Consolidate 3 TEST_CASEs into 2 SCENARIOs with SECTIONs
- Tighten tolerances: Earth 365.2105±0.1d, Mars 670.9345±0.1d
- Direction test: verify prograde rotation with 1μrad precision
- Use analytical propagation values as ground truth
- Add TOML 1.0 compliant configs (single-line inline tables)
- Update continue.md with tooling notes and TOML syntax requirements

continue.md

@@ -0,0 +1,34 @@
+# Test Refactoring Optimization Strategy
+
+## Tooling
+- `scripts/sim_engine.py` — Generic orbital mechanics simulator (Python, TOML 1.0 configs)
+  - Replicates C++ physics: Kepler propagation, orbital↔Cartesian transforms, drift detection
+  - Multi-body hierarchical propagation with global/local coordinate tracking
+  - Use for precalculating expected values (transition times, final states, energy conservation)
+- TOML configs in `tests/` must use TOML 1.0 inline table syntax (single-line `{}`)
+  - Old configs in `old_tests/` use multiline inline tables (toml-c17 style) — keep for reference
+  - Python's `tomllib` requires single-line inline tables
+
+## 1. Structure
+- One `SCENARIO("description")` per logical test group, with `[tag1][tag2]` annotations
+- Shared fixture: all constants, structs, and variables declared between `SCENARIO` opening and first `SECTION`
+- Precompute expected values analytically at fixture level (use `scripts/*.py` for complex simulations)
+
+## 2. Duplication elimination
+- Use lambdas that capture the fixture for repeated setup→call→assert patterns
+- Reuse shared structs in-place (mutate fields rather than recreating)
+- Single-line `SECTION`s when body is one statement: `SECTION("name") { helper(arg); }`
+
+## 3. Assertions
+- `using Catch::Matchers::WithinAbs;` after includes
+- `REQUIRE_THAT(value, WithinAbs(expected, tolerance))` — never `Approx()`
+- Tolerances based on actual observed errors, tightened aggressively (1e-12 for angles, 1e-6 for meters, etc.)
+- Replace qualitative checks (`a > b`) with quantitative (`WithinAbs(expected, tol)`)
+- `INFO("label: " << value)` for debugging context
+
+## 4. Process per file
+- Process **one test file at a time**.
+- For each file, **discuss with the user** how to precompute `REQUIRE` values — analytical formulas, Python scripts, or simulation runs.
+- Copy from `old_tests/` to `tests/`, rewrite, rebuild, verify.
+- **Always ask for review** before moving to the next file.
+- **Only commit when asked.**

tests/test_energy.toml

@@ -8,11 +8,7 @@ mass = 1.989e30
 radius = 6.96e8
 parent_index = -1
 color = { r = 1.0, g = 1.0, b = 0.0 }
-orbit = {
+orbit = { semi_major_axis = 0.0, eccentricity = 0.0, true_anomaly = 0.0 }
-    semi_major_axis = 0.0,
-    eccentricity = 0.0,
-    true_anomaly = 0.0
-}
 
 [[bodies]]
 name = "Earth"
@@ -20,8 +16,4 @@ mass = 5.972e24
 radius = 6.371e6
 parent_index = 0
 color = { r = 0.0, g = 0.5, b = 1.0 }
-orbit = {
+orbit = { semi_major_axis = 1.496e11, eccentricity = 0.0, true_anomaly = 0.0 }
-    semi_major_axis = 1.496e11,
-    eccentricity = 0.0,
-    true_anomaly = 0.0
-}

tests/test_orbital_period.cpp

@@ -1,81 +1,73 @@
 #include <catch2/catch_test_macros.hpp>
+#include <catch2/matchers/catch_matchers_floating_point.hpp>
 #include "../src/physics.h"
 #include "../src/simulation.h"
 #include "../src/config_loader.h"
 #include "../src/test_utilities.h"
 #include <cmath>
 
-TEST_CASE("Orbital period - Earth (RK4)", "[period][rk4]") {
+using Catch::Matchers::WithinAbs;
+
+SCENARIO("Orbital period measurement with analytical propagation",
+         "[period][analytical]") {
     const double TIME_STEP = 60.0;
-    const double EXPECTED_PERIOD_DAYS = 365.0;
     const double SECONDS_PER_DAY = 86400.0;
-    const double MAX_SIMULATION_DAYS = 400.0;
 
     SimulationState* sim = create_simulation(10, 0, 0, TIME_STEP);
-
     REQUIRE(load_system_config(sim, "tests/test_orbital_period.toml"));
 
+    SECTION("Earth completes one orbit in ~365 days") {
         OrbitTracker* tracker = create_orbit_tracker(1);
+        CelestialBody* earth = &sim->bodies[1];
+        CelestialBody* sun = &sim->bodies[0];
+
+        const double MAX_DAYS = 400.0;
+        const double max_time = MAX_DAYS * SECONDS_PER_DAY;
 
-    double max_time = MAX_SIMULATION_DAYS * SECONDS_PER_DAY;
         while (sim->time < max_time && !tracker->orbit_completed) {
             update_simulation(sim);
-        update_orbit_tracker(tracker, &sim->bodies[1], &sim->bodies[0], sim->time);
+            update_orbit_tracker(tracker, earth, sun, sim->time);
         }
 
         REQUIRE(tracker->orbit_completed);
 
-    double measured_period_days = tracker->time_at_completion / SECONDS_PER_DAY;
+        double measured_days = tracker->time_at_completion / SECONDS_PER_DAY;
-    double period_error_days = fabs(measured_period_days - EXPECTED_PERIOD_DAYS);
+        INFO("Measured period: " << measured_days << " days");
 
-    INFO("Expected period: " << EXPECTED_PERIOD_DAYS << " days");
+        REQUIRE_THAT(measured_days, WithinAbs(365.2105, 0.1));
-    INFO("Measured period: " << measured_period_days << " days");
-    INFO("Error: " << period_error_days << " days");
-
-    REQUIRE(period_error_days < 5.0);
 
         destroy_orbit_tracker(tracker);
-    destroy_simulation(sim);
     }
 
-TEST_CASE("Orbital period - Mars (RK4)", "[period][rk4]") {
+    SECTION("Mars completes one orbit in ~671 days") {
-    const double TIME_STEP = 60.0;
-    const double EXPECTED_PERIOD_DAYS = 687.0;
-    const double SECONDS_PER_DAY = 86400.0;
-    const double MAX_SIMULATION_DAYS = 750.0;
-
-    SimulationState* sim = create_simulation(10, 0, 0, TIME_STEP);
-
-    REQUIRE(load_system_config(sim, "tests/test_orbital_period.toml"));
-
         OrbitTracker* tracker = create_orbit_tracker(2);
+        CelestialBody* mars = &sim->bodies[2];
+        CelestialBody* sun = &sim->bodies[0];
+
+        const double MAX_DAYS = 750.0;
+        const double max_time = MAX_DAYS * SECONDS_PER_DAY;
 
-    double max_time = MAX_SIMULATION_DAYS * SECONDS_PER_DAY;
         while (sim->time < max_time && !tracker->orbit_completed) {
             update_simulation(sim);
-        update_orbit_tracker(tracker, &sim->bodies[2], &sim->bodies[0], sim->time);
+            update_orbit_tracker(tracker, mars, sun, sim->time);
         }
 
         REQUIRE(tracker->orbit_completed);
 
-    double measured_period_days = tracker->time_at_completion / SECONDS_PER_DAY;
+        double measured_days = tracker->time_at_completion / SECONDS_PER_DAY;
-    double period_error_days = fabs(measured_period_days - EXPECTED_PERIOD_DAYS);
+        INFO("Measured period: " << measured_days << " days");
 
-    INFO("Expected period: " << EXPECTED_PERIOD_DAYS << " days");
+        REQUIRE_THAT(measured_days, WithinAbs(670.9345, 0.1));
-    INFO("Measured period: " << measured_period_days << " days");
-    INFO("Error: " << period_error_days << " days");
-
-    REQUIRE(period_error_days < 25.0);
 
         destroy_orbit_tracker(tracker);
-    destroy_simulation(sim);
+    }
 }
 
-TEST_CASE("Orbit direction - prograde for zero inclination", "[direction]") {
+SCENARIO("Orbit direction for zero inclination",
+         "[direction][sanity]") {
     const double TIME_STEP = 60.0;
     const double TEST_DURATION_DAYS = 1.0;
-    const double SECONDS_PER_DAY = 86400.0;
+    const int STEPS = (int)(TEST_DURATION_DAYS * 86400.0 / TIME_STEP);
-    const int STEPS = (int)(TEST_DURATION_DAYS * SECONDS_PER_DAY / TIME_STEP);
 
     SimulationState* sim = create_simulation(2, 0, 0, TIME_STEP);
     REQUIRE(load_system_config(sim, "tests/test_energy.toml"));
@@ -83,20 +75,21 @@ TEST_CASE("Orbit direction - prograde for zero inclination", "[direction]") {
     CelestialBody* sun = &sim->bodies[0];
     CelestialBody* earth = &sim->bodies[1];
 
-    Vec3 initial_rel_pos = vec3_sub(earth->global_position, sun->global_position);
+    Vec3 initial_rel = vec3_sub(earth->global_position, sun->global_position);
-    double theta_start = atan2(initial_rel_pos.y, initial_rel_pos.x);
+    double theta_start = atan2(initial_rel.y, initial_rel.x);
 
     for (int i = 0; i < STEPS; i++) {
         update_simulation(sim);
     }
 
-    Vec3 final_rel_pos = vec3_sub(earth->global_position, sun->global_position);
+    Vec3 final_rel = vec3_sub(earth->global_position, sun->global_position);
-    double theta_final = atan2(final_rel_pos.y, final_rel_pos.x);
+    double theta_final = atan2(final_rel.y, final_rel.x);
+    double delta = theta_final - theta_start;
 
     INFO("Initial angle: " << theta_start << " rad");
     INFO("Final angle: " << theta_final << " rad");
+    INFO("Delta: " << delta << " rad");
 
-    REQUIRE(theta_final > theta_start);
+    REQUIRE_THAT(delta, WithinAbs(0.0172042841, 1e-6));
-
+    REQUIRE(delta > 0.0);
-    destroy_simulation(sim);
 }

tests/test_orbital_period.toml

@@ -8,11 +8,7 @@ mass = 1.989e30
 radius = 6.96e8
 parent_index = -1
 color = { r = 1.0, g = 1.0, b = 0.0 }
-orbit = {
+orbit = { semi_major_axis = 0.0, eccentricity = 0.0, true_anomaly = 0.0 }
-    semi_major_axis = 0.0,
-    eccentricity = 0.0,
-    true_anomaly = 0.0
-}
 
 [[bodies]]
 name = "Earth"
@@ -20,11 +16,7 @@ mass = 5.972e24
 radius = 6.371e6
 parent_index = 0
 color = { r = 0.0, g = 0.5, b = 1.0 }
-orbit = {
+orbit = { semi_major_axis = 1.496e11, eccentricity = 0.0, true_anomaly = 0.0 }
-    semi_major_axis = 1.496e11,
-    eccentricity = 0.0,
-    true_anomaly = 0.0
-}
 
 [[bodies]]
 name = "Mars"
@@ -32,8 +24,4 @@ mass = 6.39e23
 radius = 3.3895e6
 parent_index = 0
 color = { r = 0.8, g = 0.3, b = 0.1 }
-orbit = {
+orbit = { semi_major_axis = 2.244e11, eccentricity = 0.0, true_anomaly = 0.0 }
-    semi_major_axis = 2.244e11,
-    eccentricity = 0.0,
-    true_anomaly = 0.0
-}