import pytest

from algorithms import Algorithm, get_algorithm


def test_algorithm_has_required_methods():
    """Verify Algorithm protocol defines required methods."""
    algo = get_algorithm("pbkdf2")
    assert hasattr(algo, "hash")
    assert hasattr(algo, "verify")
    assert hasattr(algo, "identifier")


def test_get_algorithm_returns_pbkdf2():
    """Verify default algorithm is PBKDF2."""
    algo = get_algorithm("pbkdf2")
    assert algo.identifier == "pbkdf2"


def test_get_algorithm_unknown_raises_error():
    """Verify unknown algorithm raises ValueError."""
    with pytest.raises(ValueError, match="Unknown algorithm"):
        get_algorithm("unknown")