def METHOD_NAME():
    s1, s2, s3 = Square(), Square(), Square()
    anim = Succession(
        FadeIn(s1, run_time=2),
        FadeIn(s2),
        FadeIn(s3),
    )
    anim.scene = MagicMock()
    anim.run_time = 42
    anim.begin()
    anim.interpolate(0.2)
    assert anim.active_index == 0
    anim.interpolate(0.4)
    assert anim.active_index == 0
    anim.interpolate(0.6)
    assert anim.active_index == 1
    anim.interpolate(0.8)
    assert anim.active_index == 2