def test_heading(x, y, length):
a = Vector_C(x, y)
assert math.atan2(a.y, a.x) == a.heading
assert -math.pi <= a.heading <= math.pi
a.set_mag(length)
b = Vector_C().from_angle(a.heading, length=a.norm)
assert abs(a.x - b.x) < eps
assert abs(a.y - b.y) < eps
def test_set_mag(x, y, mags):
assume(x != 0)
assume(y != 0)
assume(mags)
assume(0 not in mags)
a = Vector_C(x, y)
for mag in mags:
a.set_mag(mag)
assert abs(a.norm - abs(mag)) < eps