test(tests): added test suite

The test suite is extensive. Note that LLMs were used to aid in the development of the test suite. All LLM generated code was manually reviewed.

tests/sandbox/model_sandbox.cpp

@@ -0,0 +1,67 @@
+#include <numbers>
+#include <print>
+
+#include "serif/eos/models/polytropic.hpp"
+#include "serif/equations/angular_momentum.hpp"
+#include "serif/equations/barotropic_density.hpp"
+#include "serif/equations/surface_potential.hpp"
+#include "serif/equations/mass_normalization.hpp"
+#include "serif/equations/primal_gravity.hpp"
+#include "serif/equations/registry.hpp"
+#include "serif/model/description.hpp"
+#include "serif/model/eos_reference.hpp"
+#include "serif/geometry/surface/isobaric.hpp"
+
+namespace
+{
+    namespace model = serif::model;
+    namespace equations = serif::equations;
+    namespace dimensions = serif::dimensions;
+    namespace surface = serif::geometry::surface;
+}
+
+/** @brief Inspect an explicitly chosen rotating equilibrium formulation without creating a mesh or solving it. */
+int main()
+{
+    // This list is the physical formulation. The EOS supplies relations; it does not choose equations.
+    const auto equilibrium = [](const auto& physics)
+    {
+        const auto eos = model::borrow_eos(physics.equation_of_state());
+        const auto& rotation = physics.template specification<model::FixedAngularMomentum>();
+
+        return model::EquilibriumEquations
+        {
+            .interior_equations = equations::EquationRegistry
+            {
+                equations::BarotropicDensityBalance{eos, dimensions::PressureValue{0.0}, rotation.axis(), rotation.center()},
+                equations::PrimalPoissonBalance{4.0 * std::numbers::pi},
+                equations::MassNormalization{physics.template specification<model::FixedTotalMass>().target().value()},
+                equations::AngularMomentumConstraint{rotation.target().value(), rotation.axis(), rotation.center()}
+            },
+            .shape_force = equations::SurfacePotentialBalance{rotation.axis(), rotation.center()},
+            .surface_condition = surface::Isobaric{dimensions::PressureValue{0.0}}
+        };
+    };
+
+    // Mass and angular momentum are prescribed. Density, potential, surface level, angular velocity and shape are solved.
+    const auto star = model::StellarModel
+    {
+        serif::eos::models::Polytrope{3.0, 0.25},
+        equilibrium,
+        model::FixedTotalMass{dimensions::MassValue{1.0}},
+        model::FixedAngularMomentum{dimensions::AngularMomentumValue{0.02}}
+    };
+
+    // In this example G = 1 in the chosen physical units, and scalar Poisson balance supplies gravity.
+    // Rigid rotation uses the same axis and origin in the density equation and on the pressure surface.
+    // Resolving reads immutable physics once. Keep star alive while the resolved equations borrow its EOS.
+    const auto chosen = model::resolve_equilibrium_equations(star);
+    std::println("Interior equations:");
+    chosen.interior_equations.for_each([](const auto& equation)
+    {
+        std::println("  {}", equation.name);
+    });
+    std::println("Shape equation: {}", chosen.shape_force.name);
+    std::println("Surface pressure: {}", chosen.surface_condition.target_pressure().value());
+    std::println("Prescribed mass: {}; angular momentum: {}", star.specification<model::FixedTotalMass>().target().value(), star.specification<model::FixedAngularMomentum>().target().value());
+}