def test_angle():
x = np.array([1, 0, 0])
y = np.array([0, 1, 0])
assert extra.angle(x, y) == np.pi / 2
assert extra.angle(x, x) == 0.0
assert extra.angle(x, -x) == np.pi
def test_angle(v0, v1, expected):
diff = 10e-5
assert (expected - diff) < extra.angle(v0, v1) < (expected + diff)
