public void TestRegisterSolverCallback()
{
Flex.Library lib = Flex.Init(Flex.FLEX_VERSION, ErrorCallback);
Flex.SolverDesc desc = default(Flex.SolverDesc);
Flex.SetSolverDescDefaults(ref desc);
desc.maxParticles = 1000;
desc.maxDiffuseParticles = 1000;
Flex.Solver solver = Flex.CreateSolver(lib, ref desc);
Flex.SolverCallback callback;
callback.userData = new IntPtr(1);
callback.function = (p) => { Assert.AreEqual(callback.userData, p.userData); };
Flex.SolverCallback oldCallback = Flex.RegisterSolverCallback(solver, callback, Flex.SolverCallbackStage.SubstepBegin);
Assert.AreNotEqual(callback.userData, oldCallback.userData);
Flex.DestroySolver(solver);
Flex.Shutdown(lib);
}