def test_dead_cell_with_three_neighbors_is_born():
cell = (4,5)
comfortable_world = set([cell, (3,5), (4,4), (5,5)])
assert g.cell_is_born(comfortable_world, cell) is True
def test_dead_cell_with_two_neighbors_stays_dead():
cell = (4,5)
lonely_world = set([cell, (3,5), (4,4)])
assert g.cell_is_born(lonely_world, cell) is False