/// After simulation compare the positions of points to the theoretical positions.
    bool compareSimulatedToTheoreticalPositions( double h, double tolerancePosition, double toleranceEnergy = 1e-13, double checkEnergyConservation=false)
    {
        int i = 0;
        // Init simulation
        sofa::simulation::getSimulation()->init(root.get());
        double time = root->getTime();

        // Get mechanical object
        simulation::Node::SPtr massNode = root->getChild("MassNode");
        typename MechanicalObject::SPtr dofs = massNode->get<MechanicalObject>(root->SearchDown);

        // Animate
        do
        {
            // Record the mass position
            Coord p0=dofs.get()->read(sofa::core::ConstVecCoordId::position())->getValue()[0];

            double absoluteError = fabs(p0[1]-positionsArray[i]);

            // Compare mass position to the theoretical position
            if( absoluteError > tolerancePosition )
            {
                ADD_FAILURE() << "Position of mass at time " << time << " is wrong: "  << std::endl
                    <<" expected Position is " << positionsArray[i] << std::endl
                    <<" actual Position is   " << p0[1] << std::endl
                    << "absolute error     = " << absoluteError << std::endl;
                return false;
            }

            //Animate
            sofa::simulation::getSimulation()->animate(root.get(),h);
            time = root->getTime();


            // Check if hamiltonian energy is constant when there is no damping
            if(checkEnergyConservation && fabs(variationalSolver->f_hamiltonianEnergy.getValue() -totalEnergy) > toleranceEnergy )
            {
                ADD_FAILURE() << "Hamiltonian energy at time " << time << " is wrong: "  << std::endl
                    <<" expected Energy is " << totalEnergy << std::endl
                    <<" actual Energy is   " << variationalSolver->f_hamiltonianEnergy.getValue() << std::endl
                    << "absolute error     = " << fabs(variationalSolver->f_hamiltonianEnergy.getValue() -totalEnergy) << std::endl;
                return false;
            }

            // Iterate
            i++;
        }
        while (time < 2);
        return true;
    }
    /// After simulation compare the positions of points to the theoretical positions.
    bool compareSimulatedToTheoreticalPositions(double tolerance)
    {
        // Init simulation
        sofa::simulation::getSimulation()->init(root.get());
        double time = root->getTime();
        double stiffnessSpring = 100;
        double mass = 10;
        double w = sqrt(stiffnessSpring/mass);

        // Get mechanical object
        simulation::Node::SPtr massNode = root->getChild("MassNode");
        typename MechanicalObject::SPtr dofs = massNode->get<MechanicalObject>(root->SearchDown);

        // Animate
        do
        {
            // Record the mass position
            Coord p0=dofs.get()->read(sofa::core::ConstVecCoordId::position())->getValue()[0];

            // Absolute error
            double absoluteError = fabs(p0[1]-(cos(w*time)));

            // Compare mass position to the theoretical position
            if( absoluteError > tolerance )
            {
                ADD_FAILURE() << "Position of mass at time " << time << " is wrong: "  << std::endl
                    <<" expected Position is " << cos(sqrt(stiffnessSpring/mass)*time) << std::endl
                    <<" actual Position is   " << p0[1] << std::endl
                    << "absolute error     = " << absoluteError << std::endl;
                return false;
            }

            //Animate
            sofa::simulation::getSimulation()->animate(root.get(),0.001);
            time = root->getTime();
        }
        while (time < 2);
        return true;
    }