from topo import topo_sort, has_cycle, CycleError

def test_empty():
    assert topo_sort([]) == []

def test_single():
    assert topo_sort([("a", [])]) == ["a"]

def test_linear():
    assert topo_sort([("b", ["a"]), ("c", ["b"])]) == ["a", "b", "c"]

def test_diamond():
    r = topo_sort([("d", ["b", "c"]), ("b", ["a"]), ("c", ["a"])])
    assert r[0] == "a" and r[-1] == "d"
    assert r.index("b") < r.index("c")

def test_stability():
    assert topo_sort([("x", []), ("y", []), ("z", [])]) == ["x", "y", "z"]

def test_cycle():
    try:
        topo_sort([("a", ["b"]), ("b", ["a"])])
        assert False
    except CycleError as e:
        assert set(e.remaining) == {"a", "b"}

def test_self_loop():
    assert has_cycle([("a", ["a"])])

def test_no_cycle():
    assert not has_cycle([("a", []), ("b", ["a"])])

def test_dup_preds():
    assert topo_sort([("b", ["a", "a"])]) == ["a", "b"]

if __name__ == "__main__":
    for name in [n for n in globals() if n.startswith("test_")]:
        globals()[name]()
    print("ALL TESTS PASSED")