def test_can_observe():
"""Test can_observe function used in LRB paper."""
point = Point(1.0, 1.0, 1.0, 1.0)
spacetime_loc = Point(0.0, 0.0, 0.0, 0.0)
worldline_start = Point(-10.0, -10.0, -10.0, -10.0)
worldline_end = Point(10.0, 10.0, 10.0, 10.0)
assert point.can_observe(spacetime_loc, worldline_start, worldline_end)
spacetime_loc = Point(1.0, 1.0, 1.0, 1.0)
assert point.can_observe(spacetime_loc, worldline_start, worldline_end)
