def test_group_renew():
group = Group()
u1 = Unit(1, 1)
group.addUnit(u1)
assert group.unitList == [u1]
u2 = Unit(2, 2)
group.renew([u2])
assert group.unitList == [u2]
def test_group_add_units():
group = Group()
u1 = Unit(1, 1)
u2 = Unit(2, 2)
u3 = Unit(3, 3)
group.addUnit(u1)
group.addUnit(u2)
group.addUnit(u3)
assert group.unitList == [u1, u2, u3]
assert group.getX() == 2 # mass X
assert group.getY() == 2 # mass Y
