def test_y():
a = Quaternion()
assert a.y == 0
a = Quaternion(1, 2, 3)
assert a.y == 2
a = Quaternion(4, 5, 6, 1)
assert a.y == 5
a = Quaternion(7, 8, 9)
a.y = 10
assert a.y == 10
a = Quaternion(11, 12, 13)
a.y = 14
assert a.y == 14
def test_properties():
a = Quaternion()
a.x = x
a.y = y
a.z = z
a.w = w
assert a.x == x, "Check x"
assert a.y == y, "Check y"
assert a.z == z, "Check z"
assert a.w == w, "Check w"
def test_copy():
a = Quaternion(x, y, z, w)
b = Quaternion().copy(a)
assert b.x == x
assert b.y == y
assert b.z == z
assert b.w == w
# ensure that it is a True copy
a.x = 0
a.y = -1
a.z = 0
a.w = -1
assert b.x == x
assert b.y == y