test1.py

def test():
    particles = [Particle(0.3, 0.5, +1),
                 Particle(0.0, -0.5, -1),
                 Particle(-0.1, -0.4, +3)]

    simulator = ParticleSimulator(particles)

    simulator.evolve(0.1)

    p0, p1, p2 = particles

    def fequal(a, b):
        return abs(a - b) < 1e-5

    assert fequal(p0.x, 0.2102698450356825)
    assert fequal(p0.y, 0.5438635787296997)

    assert fequal(p1.x, -0.0993347660567358)
    assert fequal(p1.y, -0.4900342888538049)

    assert fequal(p2.x, 0.1913585038252641)
    assert fequal(p2.y, -0.3652272210744360)

if __name__ == '__main__':
    test()