"""轮播视频的无 FFmpeg 依赖单测：时长策略是 API/前端说明的共同契约。"""
from __future__ import annotations

import sys
import unittest
from pathlib import Path

SERVER_DIR = Path(__file__).resolve().parents[1]
if str(SERVER_DIR) not in sys.path:
    sys.path.insert(0, str(SERVER_DIR))

from services.video_renderer import VideoRenderError, slide_seconds_for


class SlideDurationTests(unittest.TestCase):
    def test_duration_strategy_for_two_to_five_images(self) -> None:
        self.assertEqual([slide_seconds_for(count) for count in range(2, 6)], [4.5, 3.5, 3.0, 2.8])

    def test_rejects_unsupported_count(self) -> None:
        for count in (0, 1, 6):
            with self.subTest(count=count), self.assertRaises(VideoRenderError):
                slide_seconds_for(count)


if __name__ == "__main__":
    unittest.main()