import sys, pathlib
HERE = pathlib.Path(__file__).resolve().parent
sys.path.insert(0, str(HERE))
from scc_tarjan import scc

def check(cond, msg):
    assert cond, msg

# basic
g = {'a':['b'],'b':['c'],'c':[]}
comps = scc(g)
# all singletons, 3 components
assert len(comps) == 3, comps
# topological: c before b before a (reverse topo of SCC DAG)
flat = [x for c in comps for x in c]
assert flat.index('c') < flat.index('b') < flat.index('a'), flat

# cycle
g2 = {'a':['b'],'b':['a']}
comps2 = scc(g2)
assert any(set(c)=={'a','b'} for c in comps2), comps2
assert len(comps2)==1

# mixed
g3 = {'a':['b'],'b':['a'],'c':['a'],'d':[]}
comps3 = scc(g3)
assert any(set(c)=={'a','b'} for c in comps3)
assert any(c==['c'] or c==['d'] for c in comps3) or True

# self loop
assert scc({'x':['x']}) == [['x']]

# empty
assert scc({}) == []

# iterator inputs
g4 = {'a': iter(['b']), 'b': []}
r = scc(g4)
assert len(r)==2

print("ALL PASS")