test_particle.py 文件源码

def test_jitter(self):
        # Jitter cycles between +1 & -1 times time delta
        jitter_iter = itertools.cycle((1, -1))

        def jitter(dt):
            return dt * next(jitter_iter)

        physics = particle.PhysicsJitter(y=2, jitter=jitter)
        p = particle.Particle(0, 0)
        self.assertEquals(p.y, 0)

        # Jitter one second; uses jitter value 1 * 1 second * scale 2, +2 to y
        physics(1, p)
        self.assertEquals(p.y, 2)

        # Jitter 2s; uses jitter value -1 * 2 second * scale 2, -4 to y
        physics(2, p)
        self.assertEquals(p.y, -2)

        # Jitter 5s; uses jitter value 1 * 5 second * scale 2, +10 to y
        physics(5, p)
        self.assertEquals(p.y, 8)