# ABOUTME: Tests for ULID generation utility.
# ABOUTME: Verifies that generated IDs are valid 26-character ULIDs and unique.

from animaltrack.id_gen import generate_id


class TestGenerateId:
    """Tests for the generate_id function."""

    def test_returns_string(self):
        """generate_id returns a string."""
        result = generate_id()
        assert isinstance(result, str)

    def test_returns_26_characters(self):
        """generate_id returns exactly 26 characters (ULID format)."""
        result = generate_id()
        assert len(result) == 26

    def test_returns_unique_ids(self):
        """generate_id returns unique IDs on each call."""
        ids = [generate_id() for _ in range(100)]
        assert len(set(ids)) == 100

    def test_ulid_is_uppercase_alphanumeric(self):
        """ULID contains only uppercase letters and digits (Crockford base32)."""
        result = generate_id()
        # Crockford base32 excludes I, L, O, U
        valid_chars = set("0123456789ABCDEFGHJKMNPQRSTVWXYZ")
        assert all(c in valid_chars for c in result)