def test_challenge_3():
# Additional challenge: this sequence is extremely long
# Solution: 'ghi','phi','pht','pit','ait','apt','ape','age','ago','ego'
sol = ladder.solve('ghi', 'ego')
assert len(sol) == 10
assert sol[0] == 'ghi'
assert sol[-1] == 'ego'
def test_challenge_4():
# Additional challenge: return an empty list if there is no solution
# (hard version).
# Note: this is challenging because of the runtime and memory constraints
# imposed by coderpad.
sol = ladder.solve('ail', 'ism')
assert len(sol) == 0
def test_challenge_1():
# Additional challenge: return the shortest path
sol = ladder.solve('cat', 'dog')
assert_valid_sequence(sol)
assert len(sol) == 4
assert sol[0] == 'cat'
assert sol[-1] == 'dog'
def test_challenge_2():
# Additional challenge: this sequence is difficult to solve
sol = ladder.solve('man', 'ape')
assert_valid_sequence(sol)
assert len(sol) == 6
assert sol[0] == 'man'
assert sol[-1] == 'ape'
def test_several_steps():
sol = ladder.solve('cat', 'dog')
assert_valid_sequence(sol)
assert len(sol) >= 4
assert sol[0] == 'cat'
assert sol[-1] == 'dog'
def test_tricky_3():
# Additional challenge: return an empty list if there is no solution
# (easy version)
sol = ladder.solve('gnu', 'ism')
assert_valid_sequence(sol)
assert len(sol) == 0
def test_tricky_2():
sol = ladder.solve('AIL', 'ALL')
assert_valid_sequence(sol)
assert len(sol) == 2
assert sol[0].lower() == 'ail'
assert sol[-1].lower() == 'all'
def test_tricky_1():
sol = ladder.solve('all', 'all')
assert len(sol) == 1
assert sol[0] == 'all'
def test_one_step():
sol = ladder.solve('aah', 'aal')
assert_valid_sequence(sol)
assert len(sol) == 2
assert sol[0] == 'aah'
assert sol[-1] == 'aal'