def test_reflect_angle(initial: Vector, normal: Vector):
"""Test angle-related properties of Vector.reflect:
* initial.reflect(normal) * normal == - initial * normal
* normal.angle(initial) == 180 - normal.angle(reflected)
"""
# Exclude initial vectors that are very small or very close to the surface.
assume(not angle_isclose(initial.angle(normal) % 180, 90, epsilon=10))
assume(initial.length > 1e-10)
reflected = initial.reflect(normal)
assert isclose((initial * normal), -(reflected * normal))
assert angle_isclose(normal.angle(initial), 180 - normal.angle(reflected))
def test_reflect_length(initial: Vector, normal: Vector):
"""Test that reflection preserve lengths."""
assert isclose(initial.length, initial.reflect(normal).length)
def test_reflect_involutive(initial: Vector, normal: Vector):
"""Test that reflection is its own inverse
initial.reflect(normal).reflect(normal) ≃ initial
"""
assert initial.isclose(initial.reflect(normal).reflect(normal))
def test_reflect_nan_inf(initial: Vector, normal: Vector):
"""Test that reflection doesn't produce NaN or ±∞."""
assert not any(isinf(c) or isnan(c) for c in initial.reflect(normal))
