def METHOD_NAME(self):
    sim = rebound.Simulation()
    sim.add(m=1.)
    sim.add(m=1e-3, a=-1.,e=2.5)
    sim.integrator = "whfast"
    x0 = sim.energy()
    yr = -sim.particles[1].P
    sim.dt = 4.56*yr
    sim.integrate(1e3*yr)
    x1 = sim.energy()
    self.assertAlmostEqual(x0, x1, delta=1e-14)