def test_heap():
h1 = Heap()
v1 = h1.newvar()
v2 = h1.newvar()
h1.add_trail(v1)
v1.binding = 1
h2 = h1.branch()
h2.add_trail(v1)
v1.binding = 2
h2.add_trail(v2)
v2.binding = 3
h3 = h2.revert_upto(h1)
assert v1.binding == 1
assert v2.binding is None
assert h3 is h2
h1 = Heap()
h2 = h1.revert_upto(h1)
assert h2 is h1
h1 = Heap()
h2 = h1.branch()
h3 = h2.revert_upto(h1, discard_choicepoint=True)
assert h3 is h1
def test_heap_dont_trail_new():
h1 = Heap()
v1 = h1.newvar()
h1.add_trail(v1)
v1.binding = 1
h2 = h1.branch()
v2 = h2.newvar()
h2.add_trail(v1)
v1.binding = 2
h2.add_trail(v2)
v2.binding = 3
h3 = h2.revert_upto(h1)
assert v1.binding == 1
assert v2.binding == 3 # wasn't undone, because v2 dies
assert h3 is h2