def test_particle_update_pos():
p = Particle(1., 2., 3., 2., 2.)
p.update_pos(1.0)
assert p.x == 4.0
assert p.y == 5.0
p.update_pos(2.0)
assert p.x == 8.0
assert p.y == 9.0
def test_particle_update_pos__h_lt_0():
try:
p = Particle(1., 2., 2., 2., 2.)
p.update_pos(-1.0)
except ValueError:
pass