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| """Unit tests for the optional second-stage reranker (reranking.py). | |
| These cover the graceful-fallback contract (the app must never break when the | |
| reranker is disabled or unavailable) and that a working ranker actually reorders. | |
| """ | |
| import pytest | |
| from app import config, reranking | |
| from app.retrieval import ScoredChunk | |
| from tests.conftest import make_chunk | |
| try: | |
| import flashrank # noqa: F401 | |
| HAS_FLASHRANK = True | |
| except Exception: | |
| HAS_FLASHRANK = False | |
| def _scored(): | |
| # TF-IDF order: alpha(0) > bravo(1) > charlie(2) | |
| return [ | |
| ScoredChunk(make_chunk("alpha", chunk_index=0), 0.9), | |
| ScoredChunk(make_chunk("bravo", chunk_index=1), 0.5), | |
| ScoredChunk(make_chunk("charlie", chunk_index=2), 0.1), | |
| ] | |
| def test_rerank_disabled_keeps_tfidf_order(monkeypatch): | |
| monkeypatch.setattr(config, "RERANK_ENABLED", False) | |
| out = reranking.rerank("anything", _scored(), top_k=2) | |
| assert [s.chunk.chunk_index for s in out] == [0, 1] # untouched TF-IDF order, trimmed | |
| def test_rerank_unavailable_falls_back_to_tfidf(monkeypatch): | |
| # Enabled, but the ranker can't be built -> must fall back to TF-IDF order. | |
| monkeypatch.setattr(config, "RERANK_ENABLED", True) | |
| monkeypatch.setattr(reranking, "_get_ranker", lambda: None) | |
| out = reranking.rerank("anything", _scored(), top_k=2) | |
| assert [s.chunk.chunk_index for s in out] == [0, 1] | |
| def test_rerank_reorders_with_a_working_ranker(monkeypatch): | |
| # A fake ranker that promotes charlie(2) to the top proves we honour its order. | |
| monkeypatch.setattr(config, "RERANK_ENABLED", True) | |
| class FakeRanker: | |
| def rerank(self, _req): | |
| return [{"id": 2}, {"id": 0}, {"id": 1}] | |
| monkeypatch.setattr(reranking, "_get_ranker", lambda: FakeRanker()) | |
| out = reranking.rerank("anything", _scored(), top_k=2) | |
| assert [s.chunk.chunk_index for s in out] == [2, 0] | |