def test_sphere_area_sync_after_radius_update():
""" Verify volume maintains sync when radius is updated """
a_sphere = Sphere(5)
assert a_sphere.area == 314.1592653589793
a_sphere.radius = 6
assert a_sphere.area == 452.3893421169302
def test_sphere_diameter():
c = Sphere(10)
assert c.diameter == 20
c.radius = 15
assert c.diameter == 30
def test_sphere_volume_sync_after_radius_update():
""" Verify volume maintains sync when radius is updated """
a_sphere = Sphere(5)
assert a_sphere.volume == 523.5987755982989
a_sphere.radius = 6
assert a_sphere.volume == 904.7786842338603