from datetime import UTC, datetime, timedelta, timezone

import pytest

from repo_manager.time import format_utc


def test_format_utc_normalizes_offsets_and_uses_z() -> None:
    local = datetime(2026, 8, 21, 22, 30, tzinfo=timezone(timedelta(hours=2)))

    assert format_utc(local) == "2026-08-21T20:30:00Z"
    assert format_utc(local.astimezone(UTC)).endswith("Z")


def test_format_utc_rejects_naive_datetime() -> None:
    with pytest.raises(ValueError, match="timezone-aware"):
        format_utc(datetime(2026, 8, 21, 20, 30))  # noqa: DTZ001 - deliberate invalid input